diff --git a/benchmark/perf_hooks/usertiming.js b/benchmark/perf_hooks/usertiming.js
index ae797351ad78cc..24a53a116785df 100644
--- a/benchmark/perf_hooks/usertiming.js
+++ b/benchmark/perf_hooks/usertiming.js
@@ -8,24 +8,27 @@ const {
 } = require('perf_hooks');
 
 const bench = common.createBenchmark(main, {
-  n: [1e5]
+  n: [1e5],
+  observe: ['all', 'measure'],
 });
 
 function test() {
   performance.mark('a');
-  setImmediate(() => {
-    performance.mark('b');
-    performance.measure('a to b', 'a', 'b');
-  });
+  performance.mark('b');
+  performance.measure('a to b', 'a', 'b');
 }
 
-function main({ n }) {
+function main({ n, observe }) {
+  const entryTypes = observe === 'all' ?
+    [ 'mark', 'measure' ] :
+    [ observe ];
   const obs = new PerformanceObserver(() => {
     bench.end(n);
   });
-  obs.observe({ entryTypes: ['measure'], buffered: true });
+  obs.observe({ entryTypes, buffered: true });
 
   bench.start();
-  for (let i = 0; i < n; i++)
+  performance.mark('start');
+  for (let i = 0; i < 1e5; i++)
     test();
 }
diff --git a/lib/internal/errors.js b/lib/internal/errors.js
index 56a0ef8fb06a14..701a531e8cc6c5 100644
--- a/lib/internal/errors.js
+++ b/lib/internal/errors.js
@@ -1266,8 +1266,6 @@ E('ERR_INVALID_PACKAGE_TARGET',
       pkgPath}package.json${base ? ` imported from ${base}` : ''}${relError ?
       '; targets must start with "./"' : ''}`;
   }, Error);
-E('ERR_INVALID_PERFORMANCE_MARK',
-  'The "%s" performance mark has not been set', Error);
 E('ERR_INVALID_PROTOCOL',
   'Protocol "%s" not supported. Expected "%s"',
   TypeError);
diff --git a/lib/internal/perf/observe.js b/lib/internal/perf/observe.js
index 8ec8512434510b..af09d33c5405f3 100644
--- a/lib/internal/perf/observe.js
+++ b/lib/internal/perf/observe.js
@@ -4,10 +4,13 @@ const {
   ArrayFrom,
   ArrayIsArray,
   ArrayPrototypeFilter,
+  ArrayPrototypeFlatMap,
   ArrayPrototypeIncludes,
   ArrayPrototypePush,
+  ArrayPrototypePushApply,
   ArrayPrototypeSlice,
   ArrayPrototypeSort,
+  Error,
   ObjectDefineProperties,
   ObjectFreeze,
   ObjectKeys,
@@ -31,6 +34,7 @@ const {
 const {
   InternalPerformanceEntry,
   isPerformanceEntry,
+  kBufferNext,
 } = require('internal/perf/performance_entry');
 
 const {
@@ -83,6 +87,16 @@ const kSupportedEntryTypes = ObjectFreeze([
   'measure',
 ]);
 
+// Performance timeline entry Buffers
+const markEntryBuffer = createBuffer();
+const measureEntryBuffer = createBuffer();
+const kMaxPerformanceEntryBuffers = 1e6;
+const kClearPerformanceEntryBuffers = ObjectFreeze({
+  'mark': 'performance.clearMarks',
+  'measure': 'performance.clearMeasures',
+});
+const kWarnedEntryTypes = new SafeMap();
+
 const kObservers = new SafeSet();
 const kPending = new SafeSet();
 let isPending = false;
@@ -190,6 +204,7 @@ class PerformanceObserver {
     const {
       entryTypes,
       type,
+      buffered,
     } = { ...options };
     if (entryTypes === undefined && type === undefined)
       throw new ERR_MISSING_ARGS('options.entryTypes', 'options.type');
@@ -229,6 +244,13 @@ class PerformanceObserver {
         return;
       this[kEntryTypes].add(type);
       maybeIncrementObserverCount(type);
+      if (buffered) {
+        const entries = filterBufferMapByNameAndType(undefined, type);
+        ArrayPrototypePushApply(this[kBuffer], entries);
+        kPending.add(this);
+        if (kPending.size)
+          queuePending();
+      }
     }
 
     if (this[kEntryTypes].size)
@@ -291,6 +313,99 @@ function enqueue(entry) {
   for (const obs of kObservers) {
     obs[kMaybeBuffer](entry);
   }
+
+  const entryType = entry.entryType;
+  let buffer;
+  if (entryType === 'mark') {
+    buffer = markEntryBuffer;
+  } else if (entryType === 'measure') {
+    buffer = measureEntryBuffer;
+  } else {
+    return;
+  }
+
+  const count = buffer.count + 1;
+  buffer.count = count;
+  if (count === 1) {
+    buffer.head = entry;
+    buffer.tail = entry;
+    return;
+  }
+  buffer.tail[kBufferNext] = entry;
+  buffer.tail = entry;
+
+  if (count > kMaxPerformanceEntryBuffers &&
+    !kWarnedEntryTypes.has(entryType)) {
+    kWarnedEntryTypes.set(entryType, true);
+    // No error code for this since it is a Warning
+    // eslint-disable-next-line no-restricted-syntax
+    const w = new Error('Possible perf_hooks memory leak detected. ' +
+                        `${count} ${entryType} entries added to the global ` +
+                        'performance entry buffer. Use ' +
+                        `${kClearPerformanceEntryBuffers[entryType]} to ` +
+                        'clear the buffer.');
+    w.name = 'MaxPerformanceEntryBufferExceededWarning';
+    w.entryType = entryType;
+    w.count = count;
+    process.emitWarning(w);
+  }
+}
+
+function clearEntriesFromBuffer(type, name) {
+  let buffer;
+  if (type === 'mark') {
+    buffer = markEntryBuffer;
+  } else if (type === 'measure') {
+    buffer = measureEntryBuffer;
+  } else {
+    return;
+  }
+  if (name === undefined) {
+    resetBuffer(buffer);
+    return;
+  }
+
+  let head = null;
+  let tail = null;
+  for (let entry = buffer.head; entry !== null; entry = entry[kBufferNext]) {
+    if (entry.name !== name) {
+      head = head ?? entry;
+      tail = entry;
+      continue;
+    }
+    if (tail === null) {
+      continue;
+    }
+    tail[kBufferNext] = entry[kBufferNext];
+  }
+  buffer.head = head;
+  buffer.tail = tail;
+}
+
+function filterBufferMapByNameAndType(name, type) {
+  let bufferList;
+  if (type === 'mark') {
+    bufferList = [markEntryBuffer];
+  } else if (type === 'measure') {
+    bufferList = [measureEntryBuffer];
+  } else if (type !== undefined) {
+    // Unrecognized type;
+    return [];
+  } else {
+    bufferList = [markEntryBuffer, measureEntryBuffer];
+  }
+  return ArrayPrototypeFlatMap(bufferList,
+                               (buffer) => filterBufferByName(buffer, name));
+}
+
+function filterBufferByName(buffer, name) {
+  const arr = [];
+  for (let entry = buffer.head; entry !== null; entry = entry[kBufferNext]) {
+    if (name === undefined || entry.name === name) {
+      ArrayPrototypePush(arr, entry);
+    }
+  }
+  return arr;
 }
 
 function observerCallback(name, type, startTime, duration, details) {
@@ -338,8 +453,24 @@ function hasObserver(type) {
   return observerCounts[observerType] > 0;
 }
 
+function createBuffer() {
+  return {
+    head: null,
+    tail: null,
+    count: 0,
+  };
+}
+
+function resetBuffer(buffer) {
+  buffer.head = null;
+  buffer.tail = null;
+  buffer.count = 0;
+}
+
 module.exports = {
   PerformanceObserver,
   enqueue,
   hasObserver,
+  clearEntriesFromBuffer,
+  filterBufferMapByNameAndType,
 };
diff --git a/lib/internal/perf/performance.js b/lib/internal/perf/performance.js
index ca4aed90e4e270..2f75eb143a6ffe 100644
--- a/lib/internal/perf/performance.js
+++ b/lib/internal/perf/performance.js
@@ -16,8 +16,12 @@ const { now } = require('internal/perf/utils');
 const {
   mark,
   measure,
-  clearMarks,
+  clearMarkTimings,
 } = require('internal/perf/usertiming');
+const {
+  clearEntriesFromBuffer,
+  filterBufferMapByNameAndType,
+} = require('internal/perf/observe');
 
 const eventLoopUtilization = require('internal/perf/event_loop_utilization');
 const nodeTiming = require('internal/perf/nodetiming');
@@ -48,7 +52,6 @@ class Performance extends EventTarget {
       timeOrigin: this.timeOrigin,
     }, opts)}`;
   }
-
 }
 
 function toJSON() {
@@ -59,6 +62,39 @@ function toJSON() {
   };
 }
 
+function clearMarks(name) {
+  if (name !== undefined) {
+    name = `${name}`;
+  }
+  clearMarkTimings(name);
+  clearEntriesFromBuffer('mark', name);
+}
+
+function clearMeasures(name) {
+  if (name !== undefined) {
+    name = `${name}`;
+  }
+  clearEntriesFromBuffer('measure', name);
+}
+
+function getEntries() {
+  return filterBufferMapByNameAndType();
+}
+
+function getEntriesByName(name) {
+  if (name !== undefined) {
+    name = `${name}`;
+  }
+  return filterBufferMapByNameAndType(name, undefined);
+}
+
+function getEntriesByType(type) {
+  if (type !== undefined) {
+    type = `${type}`;
+  }
+  return filterBufferMapByNameAndType(undefined, type);
+}
+
 class InternalPerformance extends EventTarget {}
 InternalPerformance.prototype.constructor = Performance.prototype.constructor;
 ObjectSetPrototypeOf(InternalPerformance.prototype, Performance.prototype);
@@ -69,11 +105,31 @@ ObjectDefineProperties(Performance.prototype, {
     enumerable: false,
     value: clearMarks,
   },
+  clearMeasures: {
+    configurable: true,
+    enumerable: false,
+    value: clearMeasures,
+  },
   eventLoopUtilization: {
     configurable: true,
     enumerable: false,
     value: eventLoopUtilization,
   },
+  getEntries: {
+    configurable: true,
+    enumerable: false,
+    value: getEntries,
+  },
+  getEntriesByName: {
+    configurable: true,
+    enumerable: false,
+    value: getEntriesByName,
+  },
+  getEntriesByType: {
+    configurable: true,
+    enumerable: false,
+    value: getEntriesByType,
+  },
   mark: {
     configurable: true,
     enumerable: false,
diff --git a/lib/internal/perf/performance_entry.js b/lib/internal/perf/performance_entry.js
index f9f1c9e8966e2d..8fcb0ca3fcdc0c 100644
--- a/lib/internal/perf/performance_entry.js
+++ b/lib/internal/perf/performance_entry.js
@@ -17,6 +17,7 @@ const kType = Symbol('kType');
 const kStart = Symbol('kStart');
 const kDuration = Symbol('kDuration');
 const kDetail = Symbol('kDetail');
+const kBufferNext = Symbol('kBufferNext');
 
 function isPerformanceEntry(obj) {
   return obj?.[kName] !== undefined;
@@ -67,6 +68,7 @@ class InternalPerformanceEntry {
     this[kStart] = start;
     this[kDuration] = duration;
     this[kDetail] = detail;
+    this[kBufferNext] = null;
   }
 }
 
@@ -79,4 +81,5 @@ module.exports = {
   InternalPerformanceEntry,
   PerformanceEntry,
   isPerformanceEntry,
+  kBufferNext,
 };
diff --git a/lib/internal/perf/usertiming.js b/lib/internal/perf/usertiming.js
index f83091de1919a8..496c75deb3b78f 100644
--- a/lib/internal/perf/usertiming.js
+++ b/lib/internal/perf/usertiming.js
@@ -1,10 +1,10 @@
 'use strict';
 
 const {
-  ObjectKeys,
   SafeMap,
   SafeSet,
   SafeArrayIterator,
+  SymbolToStringTag,
 } = primordials;
 
 const { InternalPerformanceEntry } = require('internal/perf/performance_entry');
@@ -21,13 +21,14 @@ const {
 const {
   codes: {
     ERR_INVALID_ARG_VALUE,
-    ERR_INVALID_PERFORMANCE_MARK,
     ERR_PERFORMANCE_INVALID_TIMESTAMP,
     ERR_PERFORMANCE_MEASURE_INVALID_OPTIONS,
   },
 } = require('internal/errors');
 
-const marks = new SafeMap();
+const { structuredClone, lazyDOMException } = require('internal/util');
+
+const markTimings = new SafeMap();
 
 const nodeTimingReadOnlyAttributes = new SafeSet(new SafeArrayIterator([
   'nodeStart',
@@ -48,60 +49,69 @@ function getMark(name) {
   name = `${name}`;
   if (nodeTimingReadOnlyAttributes.has(name))
     return nodeTiming[name];
-  const ts = marks.get(name);
+  const ts = markTimings.get(name);
   if (ts === undefined)
-    throw new ERR_INVALID_PERFORMANCE_MARK(name);
+    throw lazyDOMException(`The "${name}" performance mark has not been set`, 'SyntaxError');
   return ts;
 }
 
 class PerformanceMark extends InternalPerformanceEntry {
-  constructor(name, options = {}) {
+  constructor(name, options) {
     name = `${name}`;
     if (nodeTimingReadOnlyAttributes.has(name))
       throw new ERR_INVALID_ARG_VALUE('name', name);
+    options ??= {};
     validateObject(options, 'options');
-    const {
-      detail,
-      startTime = now(),
-    } = options;
+    const startTime = options.startTime ?? now();
     validateNumber(startTime, 'startTime');
     if (startTime < 0)
       throw new ERR_PERFORMANCE_INVALID_TIMESTAMP(startTime);
-    marks.set(name, startTime);
+    markTimings.set(name, startTime);
+
+    let detail = options.detail;
+    detail = detail != null ?
+      structuredClone(detail) :
+      null;
     super(name, 'mark', startTime, 0, detail);
-    enqueue(this);
+  }
+
+  get [SymbolToStringTag]() {
+    return 'PerformanceMark';
   }
 }
 
 class PerformanceMeasure extends InternalPerformanceEntry {
   constructor(name, start, duration, detail) {
     super(name, 'measure', start, duration, detail);
-    enqueue(this);
+  }
+
+  get [SymbolToStringTag]() {
+    return 'PerformanceMeasure';
   }
 }
 
 function mark(name, options = {}) {
-  return new PerformanceMark(name, options);
+  const mark = new PerformanceMark(name, options);
+  enqueue(mark);
+  return mark;
 }
 
 function calculateStartDuration(startOrMeasureOptions, endMark) {
   startOrMeasureOptions ??= 0;
-  let detail;
   let start;
   let end;
   let duration;
-  if (typeof startOrMeasureOptions === 'object' &&
-      ObjectKeys(startOrMeasureOptions).length) {
-    ({
-      start,
-      end,
-      duration,
-      detail,
-    } = startOrMeasureOptions);
+  let optionsValid = false;
+  if (typeof startOrMeasureOptions === 'object') {
+    ({ start, end, duration } = startOrMeasureOptions);
+    optionsValid = start !== undefined || end !== undefined;
+  }
+  if (optionsValid) {
     if (endMark !== undefined) {
       throw new ERR_PERFORMANCE_MEASURE_INVALID_OPTIONS(
         'endMark must not be specified');
     }
+
     if (start === undefined && end === undefined) {
       throw new ERR_PERFORMANCE_MEASURE_INVALID_OPTIONS(
         'One of options.start or options.end is required');
@@ -111,21 +121,30 @@ function calculateStartDuration(startOrMeasureOptions, endMark) {
         'Must not have options.start, options.end, and ' +
         'options.duration specified');
     }
-    start = getMark(start);
-    duration = getMark(duration);
-  } else {
-    start = getMark(startOrMeasureOptions);
   }
 
-  end = getMark(endMark || end) ??
-    ((start !== undefined && duration !== undefined) ?
-      start + duration : now());
-
-  start ??= (duration !== undefined) ? end - duration : 0;
+  if (endMark !== undefined) {
+    end = getMark(endMark);
+  } else if (optionsValid && end !== undefined) {
+    end = getMark(end);
+  } else if (optionsValid && start !== undefined && duration !== undefined) {
+    end = getMark(start) + getMark(duration);
+  } else {
+    end = now();
+  }
 
-  duration ??= end - start;
+  if (typeof startOrMeasureOptions === 'string') {
+    start = getMark(startOrMeasureOptions);
+  } else if (optionsValid && start !== undefined) {
+    start = getMark(start);
+  } else if (optionsValid && duration !== undefined && end !== undefined) {
+    start = end - getMark(duration);
+  } else {
+    start = 0;
+  }
 
-  return { start, duration, detail };
+  duration = end - start;
+  return { start, duration };
 }
 
 function measure(name, startOrMeasureOptions, endMark) {
@@ -133,25 +152,29 @@ function measure(name, startOrMeasureOptions, endMark) {
   const {
     start,
     duration,
-    detail
   } = calculateStartDuration(startOrMeasureOptions, endMark);
-  return new PerformanceMeasure(name, start, duration, detail);
+  let detail = startOrMeasureOptions?.detail;
+  detail = detail != null ? structuredClone(detail) : null;
+  const measure = new PerformanceMeasure(name, start, duration, detail);
+  enqueue(measure);
+  return measure;
 }
 
-function clearMarks(name) {
+function clearMarkTimings(name) {
   if (name !== undefined) {
     name = `${name}`;
     if (nodeTimingReadOnlyAttributes.has(name))
       throw new ERR_INVALID_ARG_VALUE('name', name);
-    marks.delete(name);
+    markTimings.delete(name);
     return;
   }
-  marks.clear();
+  markTimings.clear();
 }
 
 module.exports = {
   PerformanceMark,
-  clearMarks,
+  PerformanceMeasure,
+  clearMarkTimings,
   mark,
   measure,
 };
diff --git a/lib/internal/util.js b/lib/internal/util.js
index 101fbec67775b0..9158fc8e52431e 100644
--- a/lib/internal/util.js
+++ b/lib/internal/util.js
@@ -449,6 +449,21 @@ const lazyDOMException = hideStackFrames((message, name) => {
   return new DOMException(message, name);
 });
 
+function structuredClone(value) {
+  const {
+    DefaultSerializer,
+    DefaultDeserializer,
+  } = require('v8');
+  const ser = new DefaultSerializer();
+  ser._getDataCloneError = hideStackFrames((message) =>
+    lazyDOMException(message, 'DataCloneError'));
+  ser.writeValue(value);
+  const serialized = ser.releaseBuffer();
+
+  const des = new DefaultDeserializer(serialized);
+  return des.readValue();
+}
+
 module.exports = {
   assertCrypto,
   cachedResult,
@@ -471,6 +486,7 @@ module.exports = {
   promisify,
   sleep,
   spliceOne,
+  structuredClone,
   removeColors,
 
   // Symbol used to customize promisify conversion
diff --git a/lib/perf_hooks.js b/lib/perf_hooks.js
index 339d3ca4ff0ab4..9916fd5ce40c35 100644
--- a/lib/perf_hooks.js
+++ b/lib/perf_hooks.js
@@ -10,7 +10,10 @@ const {
 
 const { PerformanceEntry } = require('internal/perf/performance_entry');
 const { PerformanceObserver } = require('internal/perf/observe');
-const { PerformanceMark } = require('internal/perf/usertiming');
+const {
+  PerformanceMark,
+  PerformanceMeasure,
+} = require('internal/perf/usertiming');
 const { InternalPerformance } = require('internal/perf/performance');
 
 const {
@@ -22,6 +25,7 @@ const monitorEventLoopDelay = require('internal/perf/event_loop_delay');
 module.exports = {
   PerformanceEntry,
   PerformanceMark,
+  PerformanceMeasure,
   PerformanceObserver,
   monitorEventLoopDelay,
   createHistogram,
diff --git a/test/common/index.js b/test/common/index.js
index 0f0885997ce9a1..2ac4538cbea804 100644
--- a/test/common/index.js
+++ b/test/common/index.js
@@ -286,6 +286,12 @@ if (global.gc) {
 if (global.performance) {
   knownGlobals.push(global.performance);
 }
+if (global.PerformanceMark) {
+  knownGlobals.push(global.PerformanceMark);
+}
+if (global.PerformanceMeasure) {
+  knownGlobals.push(global.PerformanceMeasure);
+}
 
 function allowGlobals(...allowlist) {
   knownGlobals = knownGlobals.concat(allowlist);
diff --git a/test/fixtures/wpt/LICENSE.md b/test/fixtures/wpt/LICENSE.md
index 39c46d03ac2988..ad4858c8745cfa 100644
--- a/test/fixtures/wpt/LICENSE.md
+++ b/test/fixtures/wpt/LICENSE.md
@@ -1,6 +1,6 @@
 # The 3-Clause BSD License
 
-Copyright © web-platform-tests contributors
+Copyright 2019 web-platform-tests contributors
 
 Redistribution and use in source and binary forms, with or without modification, are permitted provided that the following conditions are met:
 
diff --git a/test/fixtures/wpt/README.md b/test/fixtures/wpt/README.md
index 6019abd8aa8769..27261f56e46467 100644
--- a/test/fixtures/wpt/README.md
+++ b/test/fixtures/wpt/README.md
@@ -19,10 +19,12 @@ Last update:
 - html/webappapis/atob: https://github.com/web-platform-tests/wpt/tree/f267e1dca6/html/webappapis/atob
 - html/webappapis/microtask-queuing: https://github.com/web-platform-tests/wpt/tree/2c5c3c4c27/html/webappapis/microtask-queuing
 - html/webappapis/timers: https://github.com/web-platform-tests/wpt/tree/5873f2d8f1/html/webappapis/timers
-- interfaces: https://github.com/web-platform-tests/wpt/tree/fcb671ed8b/interfaces
+- interfaces: https://github.com/web-platform-tests/wpt/tree/80a4176623/interfaces
+- performance-timeline: https://github.com/web-platform-tests/wpt/tree/17ebc3aea0/performance-timeline
 - resources: https://github.com/web-platform-tests/wpt/tree/972ca5b669/resources
 - streams: https://github.com/web-platform-tests/wpt/tree/8f60d94439/streams
 - url: https://github.com/web-platform-tests/wpt/tree/77d54aa9e0/url
+- user-timing: https://github.com/web-platform-tests/wpt/tree/df24fb604e/user-timing
 
 [Web Platform Tests]: https://github.com/web-platform-tests/wpt
 [`git node wpt`]: https://github.com/nodejs/node-core-utils/blob/main/docs/git-node.md#git-node-wpt
diff --git a/test/fixtures/wpt/interfaces/performance-timeline.idl b/test/fixtures/wpt/interfaces/performance-timeline.idl
new file mode 100644
index 00000000000000..d3a5a278055eba
--- /dev/null
+++ b/test/fixtures/wpt/interfaces/performance-timeline.idl
@@ -0,0 +1,49 @@
+// GENERATED CONTENT - DO NOT EDIT
+// Content was automatically extracted by Reffy into webref
+// (https://github.com/w3c/webref)
+// Source: Performance Timeline Level 2 (https://w3c.github.io/performance-timeline/)
+
+partial interface Performance {
+  PerformanceEntryList getEntries ();
+  PerformanceEntryList getEntriesByType (DOMString type);
+  PerformanceEntryList getEntriesByName (DOMString name, optional DOMString type);
+};
+typedef sequence<PerformanceEntry> PerformanceEntryList;
+
+[Exposed=(Window,Worker)]
+interface PerformanceEntry {
+  readonly    attribute DOMString           name;
+  readonly    attribute DOMString           entryType;
+  readonly    attribute DOMHighResTimeStamp startTime;
+  readonly    attribute DOMHighResTimeStamp duration;
+  [Default] object toJSON();
+};
+
+callback PerformanceObserverCallback = undefined (PerformanceObserverEntryList entries,
+                                             PerformanceObserver observer,
+                                             optional PerformanceObserverCallbackOptions options = {});
+[Exposed=(Window,Worker)]
+interface PerformanceObserver {
+  constructor(PerformanceObserverCallback callback);
+  undefined observe (optional PerformanceObserverInit options = {});
+  undefined disconnect ();
+  PerformanceEntryList takeRecords();
+  [SameObject] static readonly attribute FrozenArray<DOMString> supportedEntryTypes;
+};
+
+dictionary PerformanceObserverCallbackOptions {
+  unsigned long long droppedEntriesCount;
+};
+
+dictionary PerformanceObserverInit {
+  sequence<DOMString> entryTypes;
+  DOMString type;
+  boolean buffered;
+};
+
+[Exposed=(Window,Worker)]
+interface PerformanceObserverEntryList {
+  PerformanceEntryList getEntries();
+  PerformanceEntryList getEntriesByType (DOMString type);
+  PerformanceEntryList getEntriesByName (DOMString name, optional DOMString type);
+};
diff --git a/test/fixtures/wpt/interfaces/user-timing.idl b/test/fixtures/wpt/interfaces/user-timing.idl
new file mode 100644
index 00000000000000..28ee8aac2b19a6
--- /dev/null
+++ b/test/fixtures/wpt/interfaces/user-timing.idl
@@ -0,0 +1,34 @@
+// GENERATED CONTENT - DO NOT EDIT
+// Content was automatically extracted by Reffy into webref
+// (https://github.com/w3c/webref)
+// Source: User Timing Level 3 (https://w3c.github.io/user-timing/)
+
+dictionary PerformanceMarkOptions {
+    any detail;
+    DOMHighResTimeStamp startTime;
+};
+
+dictionary PerformanceMeasureOptions {
+    any detail;
+    (DOMString or DOMHighResTimeStamp) start;
+    DOMHighResTimeStamp duration;
+    (DOMString or DOMHighResTimeStamp) end;
+};
+
+partial interface Performance {
+    PerformanceMark mark(DOMString markName, optional PerformanceMarkOptions markOptions = {});
+    undefined clearMarks(optional DOMString markName);
+    PerformanceMeasure measure(DOMString measureName, optional (DOMString or PerformanceMeasureOptions) startOrMeasureOptions = {}, optional DOMString endMark);
+    undefined clearMeasures(optional DOMString measureName);
+};
+
+[Exposed=(Window,Worker)]
+interface PerformanceMark : PerformanceEntry {
+  constructor(DOMString markName, optional PerformanceMarkOptions markOptions = {});
+  readonly attribute any detail;
+};
+
+[Exposed=(Window,Worker)]
+interface PerformanceMeasure : PerformanceEntry {
+  readonly attribute any detail;
+};
diff --git a/test/fixtures/wpt/performance-timeline/META.yml b/test/fixtures/wpt/performance-timeline/META.yml
new file mode 100644
index 00000000000000..89fae1db0d9b7a
--- /dev/null
+++ b/test/fixtures/wpt/performance-timeline/META.yml
@@ -0,0 +1,4 @@
+spec: https://w3c.github.io/performance-timeline/
+suggested_reviewers:
+  - plehegar
+  - igrigorik
diff --git a/test/fixtures/wpt/performance-timeline/buffered-flag-after-timeout.any.js b/test/fixtures/wpt/performance-timeline/buffered-flag-after-timeout.any.js
new file mode 100644
index 00000000000000..08b3e323146585
--- /dev/null
+++ b/test/fixtures/wpt/performance-timeline/buffered-flag-after-timeout.any.js
@@ -0,0 +1,11 @@
+async_test(t => {
+  performance.mark('foo');
+  t.step_timeout(() => {
+    // After a timeout, PerformanceObserver should still receive entry if using the buffered flag.
+    new PerformanceObserver(t.step_func_done(list => {
+      const entries = list.getEntries();
+      assert_equals(entries.length, 1, 'There should be 1 mark entry.');
+      assert_equals(entries[0].entryType, 'mark');
+    })).observe({type: 'mark', buffered: true});
+  }, 100);
+}, 'PerformanceObserver with buffered flag sees entry after timeout');
diff --git a/test/fixtures/wpt/performance-timeline/buffered-flag-observer.any.js b/test/fixtures/wpt/performance-timeline/buffered-flag-observer.any.js
new file mode 100644
index 00000000000000..31dc39c128ad55
--- /dev/null
+++ b/test/fixtures/wpt/performance-timeline/buffered-flag-observer.any.js
@@ -0,0 +1,15 @@
+async_test( t=> {
+  for (let i = 0; i < 50; i++)
+    performance.mark('foo' + i);
+  let marksCreated = 50;
+  let marksReceived = 0;
+  new PerformanceObserver(list => {
+    marksReceived += list.getEntries().length;
+    if (marksCreated < 100) {
+      performance.mark('bar' + marksCreated);
+      marksCreated++;
+    }
+    if (marksReceived == 100)
+      t.done();
+  }).observe({type: 'mark', buffered: true});
+}, 'PerformanceObserver with buffered flag should see past and future entries.');
diff --git a/test/fixtures/wpt/performance-timeline/case-sensitivity.any.js b/test/fixtures/wpt/performance-timeline/case-sensitivity.any.js
new file mode 100644
index 00000000000000..3a98505ae67f7d
--- /dev/null
+++ b/test/fixtures/wpt/performance-timeline/case-sensitivity.any.js
@@ -0,0 +1,64 @@
+  test(function () {
+    assert_equals(typeof self.performance, "object");
+    assert_equals(typeof self.performance.getEntriesByType, "function");
+    var lowerList = self.performance.getEntriesByType("resource");
+    var upperList = self.performance.getEntriesByType("RESOURCE");
+    var mixedList = self.performance.getEntriesByType("ReSoUrCe");
+
+    assert_not_equals(lowerList.length, 0, "Resource entries exist");
+    assert_equals(upperList.length, 0, "getEntriesByType('RESOURCE').length");
+    assert_equals(mixedList.length, 0, "getEntriesByType('ReSoUrCe').length");
+
+  }, "getEntriesByType values are case sensitive");
+
+  test(function () {
+    assert_equals(typeof self.performance, "object");
+    assert_equals(typeof self.performance.getEntriesByName, "function");
+    var origin = self.location.protocol + "//" + self.location.host;
+    var location1 = origin.toUpperCase() + "/resources/testharness.js";
+    var location2 = self.location.protocol + "//"
+     + self.location.host.toUpperCase() + "/resources/testharness.js";
+    var lowerList = self.performance.getEntriesByName(origin + "/resources/testharness.js");
+    var upperList = self.performance.getEntriesByName(location1);
+    var mixedList = self.performance.getEntriesByName(location2);
+
+    assert_equals(lowerList.length, 1, "Resource entry exist");
+    assert_equals(upperList.length, 0, "getEntriesByName('" + location1 + "').length");
+    assert_equals(mixedList.length, 0, "getEntriesByName('" + location2 + "').length");
+
+  }, "getEntriesByName values are case sensitive");
+
+  async_test(function (t) {
+    // Test type/buffered case sensitivity.
+    observer = new PerformanceObserver(
+      t.step_func(function (entryList, obs) {
+        assert_unreached("Observer(type) should not be called.");
+      })
+    );
+    observer.observe({type: "Mark"});
+    observer.observe({type: "Measure"});
+    observer.observe({type: "MARK"});
+    observer.observe({type: "MEASURE"});
+    observer.observe({type: "Mark", buffered: true});
+    observer.observe({type: "Measure", buffered: true});
+    observer.observe({type: "MARK", buffered: true});
+    observer.observe({type: "MEASURE", buffered: true});
+    self.performance.mark("mark1");
+    self.performance.measure("measure1");
+
+    // Test entryTypes case sensitivity.
+    observer = new PerformanceObserver(
+      t.step_func(function (entryList, obs) {
+        assert_unreached("Observer(entryTypes) should not be called.");
+      })
+    );
+    observer.observe({entryTypes: ["Mark", "Measure"]});
+    observer.observe({entryTypes: ["MARK", "MEASURE"]});
+    self.performance.mark("mark1");
+    self.performance.measure("measure1");
+
+    t.step_timeout(function() {
+      t.done();
+    }, 1000);
+
+  }, "observe() and case sensitivity for types/entryTypes and buffered.");
diff --git a/test/fixtures/wpt/performance-timeline/get-invalid-entries.html b/test/fixtures/wpt/performance-timeline/get-invalid-entries.html
new file mode 100644
index 00000000000000..33d6589e275e26
--- /dev/null
+++ b/test/fixtures/wpt/performance-timeline/get-invalid-entries.html
@@ -0,0 +1,27 @@
+<!doctype html>
+<html>
+<head>
+<script src="/resources/testharness.js"></script>
+<script src="/resources/testharnessreport.js"></script>
+</head>
+<body>
+<script>
+async_test(function(t) {
+  performance.mark('windowMark');
+  const worker = new Worker("resources/worker-invalid-entries.js");
+  worker.onmessage = function(event) {
+    assert_equals(event.data['invalid'], 0, 'The worker must have 0 invalid entries.');
+    assert_equals(event.data['mark'], 1, 'The worker must have 1 mark entry.');
+    assert_equals(event.data['measure'], 0, 'The worker must have 0 measure entries.');
+    assert_equals(performance.getEntriesByType('invalid').length, 0,
+      'The window must have 0 invalid entries.');
+    assert_equals(performance.getEntriesByType('mark').length, 1,
+      'The window must have 1 mark entry.');
+    assert_equals(performance.getEntriesByType('measure').length, 0,
+      'The window must have 0 measure entries.')
+    t.done();
+  }
+}, 'Get invalid entries from worker and window.');
+</script>
+</body>
+</html>
diff --git a/test/fixtures/wpt/performance-timeline/idlharness.any.js b/test/fixtures/wpt/performance-timeline/idlharness.any.js
new file mode 100644
index 00000000000000..32efebe98ffd47
--- /dev/null
+++ b/test/fixtures/wpt/performance-timeline/idlharness.any.js
@@ -0,0 +1,25 @@
+// META: global=window,worker
+// META: script=/resources/WebIDLParser.js
+// META: script=/resources/idlharness.js
+
+// https://w3c.github.io/performance-timeline/
+
+'use strict';
+
+idl_test(
+  ['performance-timeline'],
+  ['hr-time', 'dom'],
+  async idl_array => {
+    idl_array.add_objects({
+      Performance: ['performance'],
+      PerformanceObserver: ['observer'],
+      PerformanceObserverEntryList: ['entryList'],
+    });
+
+    self.entryList = await new Promise((resolve, reject) => {
+      self.observer = new PerformanceObserver(resolve);
+      observer.observe({ entryTypes: ['mark'] });
+      performance.mark('test');
+    });
+  }
+);
diff --git a/test/fixtures/wpt/performance-timeline/multiple-buffered-flag-observers.any.js b/test/fixtures/wpt/performance-timeline/multiple-buffered-flag-observers.any.js
new file mode 100644
index 00000000000000..5dd44fb18fbdb9
--- /dev/null
+++ b/test/fixtures/wpt/performance-timeline/multiple-buffered-flag-observers.any.js
@@ -0,0 +1,32 @@
+promise_test(() => {
+  // The first promise waits for one buffered flag observer to receive 3 entries.
+  const promise1 = new Promise(resolve1 => {
+    let numObserved1 = 0;
+    new PerformanceObserver((entryList, obs) => {
+      // This buffered flag observer is constructed after a regular observer detects a mark.
+      new PerformanceObserver(list => {
+        numObserved1 += list.getEntries().length;
+        if (numObserved1 == 3)
+          resolve1();
+      }).observe({type: 'mark', buffered: true});
+      obs.disconnect();
+    }).observe({entryTypes: ['mark']});
+    performance.mark('foo');
+  });
+  // The second promise waits for another buffered flag observer to receive 3 entries.
+  const promise2 = new Promise(resolve2 => {
+    step_timeout(() => {
+      let numObserved2 = 0;
+      // This buffered flag observer is constructed after a delay of 100ms.
+      new PerformanceObserver(list => {
+        numObserved2 += list.getEntries().length;
+        if (numObserved2 == 3)
+          resolve2();
+      }).observe({type: 'mark', buffered: true});
+    }, 100);
+    performance.mark('bar');
+  });
+  performance.mark('meow');
+  // Pass if and only if both buffered observers received all 3 mark entries.
+  return Promise.all([promise1, promise2]);
+}, 'Multiple PerformanceObservers with buffered flag see all entries');
diff --git a/test/fixtures/wpt/performance-timeline/not-clonable.html b/test/fixtures/wpt/performance-timeline/not-clonable.html
new file mode 100644
index 00000000000000..d651776e5f4b94
--- /dev/null
+++ b/test/fixtures/wpt/performance-timeline/not-clonable.html
@@ -0,0 +1,10 @@
+<!doctype html>
+<script src="/resources/testharness.js"></script>
+<script src="/resources/testharnessreport.js"></script>
+<script>
+  const t = async_test("Test that a postMessage of a performance entry fails");
+  addEventListener("message", t.step_func_done(e => {
+    assert_equals(e.data, "PASS");
+  }));
+</script>
+<iframe src="resources/postmessage-entry.html"></iframe>
diff --git a/test/fixtures/wpt/performance-timeline/observer-buffered-false.any.js b/test/fixtures/wpt/performance-timeline/observer-buffered-false.any.js
new file mode 100644
index 00000000000000..a28100b0fdba2e
--- /dev/null
+++ b/test/fixtures/wpt/performance-timeline/observer-buffered-false.any.js
@@ -0,0 +1,12 @@
+async_test(t => {
+  performance.mark('foo');
+  // Use a timeout to ensure the remainder of the test runs after the entry is created.
+  t.step_timeout(() => {
+    // Observer with buffered flag set to false should not see entry.
+    new PerformanceObserver(() => {
+      assert_unreached('Should not have observed any entry!');
+    }).observe({type: 'mark', buffered: false});
+    // Use a timeout to give time to the observer.
+    t.step_timeout(t.step_func_done(() => {}), 100);
+  }, 0);
+}, 'PerformanceObserver without buffered flag set to false cannot see past entries.');
diff --git a/test/fixtures/wpt/performance-timeline/performanceentry-tojson.any.js b/test/fixtures/wpt/performance-timeline/performanceentry-tojson.any.js
new file mode 100644
index 00000000000000..44f0156eec1924
--- /dev/null
+++ b/test/fixtures/wpt/performance-timeline/performanceentry-tojson.any.js
@@ -0,0 +1,21 @@
+test(() => {
+  performance.mark('markName');
+  performance.measure('measureName');
+
+  const entries = performance.getEntries();
+  const performanceEntryKeys = [
+    'name',
+    'entryType',
+    'startTime',
+    'duration'
+  ];
+  for (let i = 0; i < entries.length; ++i) {
+    assert_equals(typeof(entries[i].toJSON), 'function');
+    const json = entries[i].toJSON();
+    assert_equals(typeof(json), 'object');
+    for (const key of performanceEntryKeys) {
+      assert_equals(json[key], entries[i][key],
+        `entries[${i}].toJSON().${key} should match entries[${i}].${key}`);
+    }
+  }
+}, 'Test toJSON() in PerformanceEntry');
diff --git a/test/fixtures/wpt/performance-timeline/performanceobservers.js b/test/fixtures/wpt/performance-timeline/performanceobservers.js
new file mode 100644
index 00000000000000..3f357374efdfc2
--- /dev/null
+++ b/test/fixtures/wpt/performance-timeline/performanceobservers.js
@@ -0,0 +1,44 @@
+// Compares a performance entry to a predefined one
+// perfEntriesToCheck is an array of performance entries from the user agent
+// expectedEntries is an array of performance entries minted by the test
+function checkEntries(perfEntriesToCheck, expectedEntries) {
+  function findMatch(pe) {
+    // we match based on entryType and name
+    for (var i = expectedEntries.length - 1; i >= 0; i--) {
+      var ex = expectedEntries[i];
+      if (ex.entryType === pe.entryType && ex.name === pe.name) {
+        return ex;
+      }
+    }
+    return null;
+  }
+
+  assert_equals(perfEntriesToCheck.length, expectedEntries.length, "performance entries must match");
+
+  perfEntriesToCheck.forEach(function (pe1) {
+    assert_not_equals(findMatch(pe1), null, "Entry matches");
+  });
+}
+
+// Waits for performance.now to advance. Since precision reduction might
+// cause it to return the same value across multiple calls.
+function wait() {
+  var now = performance.now();
+  while (now === performance.now())
+    continue;
+}
+
+// Ensure the entries list is sorted by startTime.
+function checkSorted(entries) {
+  assert_not_equals(entries.length, 0, "entries list must not be empty");
+  if (!entries.length)
+    return;
+
+  var sorted = false;
+  var lastStartTime = entries[0].startTime;
+  for (var i = 1; i < entries.length; ++i) {
+    var currStartTime = entries[i].startTime;
+    assert_less_than_equal(lastStartTime, currStartTime, "entry list must be sorted by startTime");
+    lastStartTime = currStartTime;
+  }
+}
diff --git a/test/fixtures/wpt/performance-timeline/po-callback-mutate.any.js b/test/fixtures/wpt/performance-timeline/po-callback-mutate.any.js
new file mode 100644
index 00000000000000..8f1b09bc377120
--- /dev/null
+++ b/test/fixtures/wpt/performance-timeline/po-callback-mutate.any.js
@@ -0,0 +1,66 @@
+// META: script=performanceobservers.js
+
+  async_test(function (t) {
+    var callbackCount = 0;
+    var observer = new PerformanceObserver(
+        t.step_func(function (entryList, obs) {
+          callbackCount++;
+
+          if (callbackCount === 1) {
+            checkEntries(entryList.getEntries(), [
+              {entryType: "measure", name: "measure1"},
+            ]);
+            observer.observe({entryTypes: ["mark"]});
+            self.performance.mark("mark2");
+            self.performance.measure("measure2");
+            return;
+          }
+
+          if (callbackCount === 2) {
+            checkEntries(entryList.getEntries(), [
+              {entryType: "mark", name: "mark2"},
+            ]);
+            self.performance.mark("mark-before-change-observe-state-to-measure");
+            self.performance.measure("measure-before-change-observe-state-to-measure");
+            observer.observe({entryTypes: ["measure"]});
+            self.performance.mark("mark3");
+            self.performance.measure("measure3");
+            return;
+          }
+
+          if (callbackCount === 3) {
+            checkEntries(entryList.getEntries(), [
+              {entryType: "measure", name: "measure3"},
+              {entryType: "mark", name: "mark-before-change-observe-state-to-measure"},
+            ]);
+            self.performance.mark("mark-before-change-observe-state-to-both");
+            self.performance.measure("measure-before-change-observe-state-to-both");
+            observer.observe({entryTypes: ["mark", "measure"]});
+            self.performance.mark("mark4");
+            self.performance.measure("measure4");
+            return;
+          }
+
+          if (callbackCount === 4) {
+            checkEntries(entryList.getEntries(), [
+              {entryType: "measure", name: "measure-before-change-observe-state-to-both"},
+              {entryType: "measure", name: "measure4"},
+              {entryType: "mark", name: "mark4"},
+            ]);
+            self.performance.mark("mark-before-disconnect");
+            self.performance.measure("measure-before-disconnect");
+            observer.disconnect();
+            self.performance.mark("mark-after-disconnect");
+            self.performance.measure("measure-after-disconnect");
+            t.done();
+            return;
+          }
+
+          assert_unreached("The callback must not be invoked after disconnecting");
+        })
+      );
+
+    observer.observe({entryTypes: ["measure"]});
+    self.performance.mark("mark1");
+    self.performance.measure("measure1");
+  }, "PerformanceObserver modifications inside callback should update filtering and not clear buffer");
diff --git a/test/fixtures/wpt/performance-timeline/po-disconnect-removes-observed-types.any.js b/test/fixtures/wpt/performance-timeline/po-disconnect-removes-observed-types.any.js
new file mode 100644
index 00000000000000..cac97bea0755c1
--- /dev/null
+++ b/test/fixtures/wpt/performance-timeline/po-disconnect-removes-observed-types.any.js
@@ -0,0 +1,19 @@
+// META: script=performanceobservers.js
+
+async_test(function (t) {
+  const observer  = new PerformanceObserver(
+      t.step_func(function (entryList) {
+        // There should be no mark entry.
+        checkEntries(entryList.getEntries(),
+          [{ entryType: "measure", name: "b"}]);
+        t.done();
+      })
+    );
+  observer.observe({type: "mark"});
+  // Disconnect the observer.
+  observer.disconnect();
+  // Now, only observe measure.
+  observer.observe({type: "measure"});
+  performance.mark("a");
+  performance.measure("b");
+}, "Types observed are forgotten when disconnect() is called.");
diff --git a/test/fixtures/wpt/performance-timeline/po-disconnect.any.js b/test/fixtures/wpt/performance-timeline/po-disconnect.any.js
new file mode 100644
index 00000000000000..5f5fb5aa43ba46
--- /dev/null
+++ b/test/fixtures/wpt/performance-timeline/po-disconnect.any.js
@@ -0,0 +1,37 @@
+// META: script=performanceobservers.js
+
+  async_test(function (t) {
+    var observer = new PerformanceObserver(
+        t.step_func(function (entryList, obs) {
+          assert_unreached("This callback must not be invoked");
+        })
+      );
+    observer.observe({entryTypes: ["mark", "measure", "navigation"]});
+    observer.disconnect();
+    self.performance.mark("mark1");
+    self.performance.measure("measure1");
+    t.step_timeout(function () {
+      t.done();
+    }, 2000);
+  }, "disconnected callbacks must not be invoked");
+
+  test(function () {
+    var obs = new PerformanceObserver(function () { return true; });
+    obs.disconnect();
+    obs.disconnect();
+  }, "disconnecting an unconnected observer is a no-op");
+
+  async_test(function (t) {
+    var observer = new PerformanceObserver(
+        t.step_func(function (entryList, obs) {
+          assert_unreached("This callback must not be invoked");
+        })
+      );
+    observer.observe({entryTypes: ["mark"]});
+    self.performance.mark("mark1");
+    observer.disconnect();
+    self.performance.mark("mark2");
+    t.step_timeout(function () {
+      t.done();
+    }, 2000);
+  }, "An observer disconnected after a mark must not have its callback invoked");
diff --git a/test/fixtures/wpt/performance-timeline/po-entries-sort.any.js b/test/fixtures/wpt/performance-timeline/po-entries-sort.any.js
new file mode 100644
index 00000000000000..b0c781a3c0c03b
--- /dev/null
+++ b/test/fixtures/wpt/performance-timeline/po-entries-sort.any.js
@@ -0,0 +1,64 @@
+// META: script=performanceobservers.js
+
+  async_test(function (t) {
+    var stored_entries = [];
+    var stored_entries_by_type = [];
+    var observer = new PerformanceObserver(
+        t.step_func(function (entryList, obs) {
+
+          stored_entries = entryList.getEntries();
+          stored_entries_by_type = entryList.getEntriesByType("mark");
+          stored_entries_by_name = entryList.getEntriesByName("name-repeat");
+          var startTimeOfMark2 = entryList.getEntriesByName("mark2")[0].startTime;
+
+          checkSorted(stored_entries);
+          checkEntries(stored_entries, [
+            {entryType: "measure", name: "measure1"},
+            {entryType: "measure", name: "measure2"},
+            {entryType: "measure", name: "measure3"},
+            {entryType: "measure", name: "name-repeat"},
+            {entryType: "mark", name: "mark1"},
+            {entryType: "mark", name: "mark2"},
+            {entryType: "measure", name: "measure-matching-mark2-1"},
+            {entryType: "measure", name: "measure-matching-mark2-2"},
+            {entryType: "mark", name: "name-repeat"},
+            {entryType: "mark", name: "name-repeat"},
+          ]);
+
+          checkSorted(stored_entries_by_type);
+          checkEntries(stored_entries_by_type, [
+            {entryType: "mark", name: "mark1"},
+            {entryType: "mark", name: "mark2"},
+            {entryType: "mark", name: "name-repeat"},
+            {entryType: "mark", name: "name-repeat"},
+          ]);
+
+          checkSorted(stored_entries_by_name);
+          checkEntries(stored_entries_by_name, [
+            {entryType: "measure", name: "name-repeat"},
+            {entryType: "mark", name: "name-repeat"},
+            {entryType: "mark", name: "name-repeat"},
+          ]);
+
+          observer.disconnect();
+          t.done();
+        })
+      );
+
+    observer.observe({entryTypes: ["mark", "measure"]});
+
+    self.performance.mark("mark1");
+    self.performance.measure("measure1");
+    wait(); // Ensure mark1 !== mark2 startTime by making sure performance.now advances.
+    self.performance.mark("mark2");
+    self.performance.measure("measure2");
+    self.performance.measure("measure-matching-mark2-1", "mark2");
+    wait(); // Ensure mark2 !== mark3 startTime by making sure performance.now advances.
+    self.performance.mark("name-repeat");
+    self.performance.measure("measure3");
+    self.performance.measure("measure-matching-mark2-2", "mark2");
+    wait(); // Ensure name-repeat startTime will differ.
+    self.performance.mark("name-repeat");
+    wait(); // Ensure name-repeat startTime will differ.
+    self.performance.measure("name-repeat");
+  }, "getEntries, getEntriesByType, getEntriesByName sort order");
diff --git a/test/fixtures/wpt/performance-timeline/po-getentries.any.js b/test/fixtures/wpt/performance-timeline/po-getentries.any.js
new file mode 100644
index 00000000000000..36169d5dbd6e0e
--- /dev/null
+++ b/test/fixtures/wpt/performance-timeline/po-getentries.any.js
@@ -0,0 +1,38 @@
+// META: script=performanceobservers.js
+
+  async_test(function (t) {
+    var observer = new PerformanceObserver(
+        t.step_func(function (entryList, obs) {
+          checkEntries(entryList.getEntries(),
+            [{ entryType: "mark", name: "mark1"}], "getEntries");
+
+          checkEntries(entryList.getEntriesByType("mark"),
+            [{ entryType: "mark", name: "mark1"}], "getEntriesByType");
+          assert_equals(entryList.getEntriesByType("measure").length, 0,
+           "getEntriesByType with no expected entry");
+          assert_equals(entryList.getEntriesByType("234567").length, 0,
+           "getEntriesByType with no expected entry");
+
+          checkEntries(entryList.getEntriesByName("mark1"),
+            [{ entryType: "mark", name: "mark1"}], "getEntriesByName");
+          assert_equals(entryList.getEntriesByName("mark2").length, 0,
+            "getEntriesByName with no expected entry");
+          assert_equals(entryList.getEntriesByName("234567").length, 0,
+            "getEntriesByName with no expected entry");
+
+          checkEntries(entryList.getEntriesByName("mark1", "mark"),
+            [{ entryType: "mark", name: "mark1"}], "getEntriesByName with a type");
+          assert_equals(entryList.getEntriesByName("mark1", "measure").length, 0,
+            "getEntriesByName with a type with no expected entry");
+          assert_equals(entryList.getEntriesByName("mark2", "measure").length, 0,
+            "getEntriesByName with a type with no expected entry");
+          assert_equals(entryList.getEntriesByName("mark1", "234567").length, 0,
+            "getEntriesByName with a type with no expected entry");
+
+          observer.disconnect();
+          t.done();
+        })
+      );
+    observer.observe({entryTypes: ["mark"]});
+    self.performance.mark("mark1");
+  }, "getEntries, getEntriesByType and getEntriesByName work");
diff --git a/test/fixtures/wpt/performance-timeline/po-mark-measure.any.js b/test/fixtures/wpt/performance-timeline/po-mark-measure.any.js
new file mode 100644
index 00000000000000..0b205e094c75e1
--- /dev/null
+++ b/test/fixtures/wpt/performance-timeline/po-mark-measure.any.js
@@ -0,0 +1,61 @@
+// META: script=performanceobservers.js
+
+  async_test(function (t) {
+    var stored_entries = [];
+    var observer  = new PerformanceObserver(
+        t.step_func(function (entryList, obs) {
+          stored_entries =
+            stored_entries.concat(entryList.getEntries());
+          if (stored_entries.length >= 4) {
+            checkEntries(stored_entries,
+              [{ entryType: "mark", name: "mark1"},
+              { entryType: "mark", name: "mark2"},
+              { entryType: "measure", name: "measure1"},
+              { entryType: "measure", name: "measure2"}]);
+            observer.disconnect();
+            t.done();
+          }
+        })
+      );
+    observer.observe({entryTypes: ["mark", "measure"]});
+  }, "entries are observable");
+
+  async_test(function (t) {
+    var mark_entries = [];
+    var observer = new PerformanceObserver(
+        t.step_func(function (entryList, obs) {
+          mark_entries =
+            mark_entries.concat(entryList.getEntries());
+          if (mark_entries.length >= 2) {
+            checkEntries(mark_entries,
+              [{ entryType: "mark", name: "mark1"},
+              { entryType: "mark", name: "mark2"}]);
+            observer.disconnect();
+            t.done();
+          }
+        })
+      );
+    observer.observe({entryTypes: ["mark"]});
+    self.performance.mark("mark1");
+    self.performance.mark("mark2");
+  }, "mark entries are observable");
+
+  async_test(function (t) {
+    var measure_entries = [];
+    var observer = new PerformanceObserver(
+        t.step_func(function (entryList, obs) {
+          measure_entries =
+            measure_entries.concat(entryList.getEntries());
+          if (measure_entries.length >= 2) {
+            checkEntries(measure_entries,
+              [{ entryType: "measure", name: "measure1"},
+              { entryType: "measure", name: "measure2"}]);
+            observer.disconnect();
+            t.done();
+          }
+        })
+      );
+    observer.observe({entryTypes: ["measure"]});
+    self.performance.measure("measure1");
+    self.performance.measure("measure2");
+  }, "measure entries are observable");
diff --git a/test/fixtures/wpt/performance-timeline/po-observe-repeated-type.any.js b/test/fixtures/wpt/performance-timeline/po-observe-repeated-type.any.js
new file mode 100644
index 00000000000000..2bba396a6b69eb
--- /dev/null
+++ b/test/fixtures/wpt/performance-timeline/po-observe-repeated-type.any.js
@@ -0,0 +1,17 @@
+// META: script=performanceobservers.js
+
+async_test(function (t) {
+  const observer  = new PerformanceObserver(
+      t.step_func(function (entryList) {
+        checkEntries(entryList.getEntries(),
+          [{ entryType: "mark", name: "early"}]);
+        observer.disconnect();
+        t.done();
+      })
+    );
+  performance.mark("early");
+  // This call will not trigger anything.
+  observer.observe({type: "mark"});
+  // This call should override the previous call and detect the early mark.
+  observer.observe({type: "mark", buffered: true});
+}, "Two calls of observe() with the same 'type' cause override.");
diff --git a/test/fixtures/wpt/performance-timeline/po-observe-type.any.js b/test/fixtures/wpt/performance-timeline/po-observe-type.any.js
new file mode 100644
index 00000000000000..b9854cc1466fa7
--- /dev/null
+++ b/test/fixtures/wpt/performance-timeline/po-observe-type.any.js
@@ -0,0 +1,64 @@
+// META: script=performanceobservers.js
+
+test(function () {
+  const obs = new PerformanceObserver(() => {});
+  assert_throws_js(TypeError, function () {
+    obs.observe({});
+  });
+  assert_throws_js(TypeError, function () {
+    obs.observe({entryType: ['mark', 'measure']});
+  });
+}, "Calling observe() without 'type' or 'entryTypes' throws a TypeError");
+
+test(() => {
+  const obs = new PerformanceObserver(() =>{});
+  obs.observe({entryTypes: ["mark"]});
+  assert_throws_dom('InvalidModificationError', function () {
+    obs.observe({type: "measure"});
+  });
+}, "Calling observe() with entryTypes and then type should throw an InvalidModificationError");
+
+test(() => {
+  const obs = new PerformanceObserver(() =>{});
+  obs.observe({type: "mark"});
+  assert_throws_dom('InvalidModificationError', function () {
+    obs.observe({entryTypes: ["measure"]});
+  });
+}, "Calling observe() with type and then entryTypes should throw an InvalidModificationError");
+
+test(() => {
+  const obs = new PerformanceObserver(() =>{});
+  assert_throws_js(TypeError, function () {
+    obs.observe({type: "mark", entryTypes: ["measure"]});
+  });
+}, "Calling observe() with type and entryTypes should throw a TypeError");
+
+test(function () {
+  const obs = new PerformanceObserver(() =>{});
+  // Definitely not an entry type.
+  obs.observe({type: "this-cannot-match-an-entryType"});
+  // Close to an entry type, but not quite.
+  obs.observe({type: "marks"});
+}, "Passing in unknown values to type does throw an exception.");
+
+async_test(function (t) {
+  let observedMark = false;
+  let observedMeasure = false;
+  const observer = new PerformanceObserver(
+    t.step_func(function (entryList, obs) {
+      observedMark |= entryList.getEntries().filter(
+        entry => entry.entryType === 'mark').length;
+      observedMeasure |= entryList.getEntries().filter(
+        entry => entry.entryType === 'measure').length
+      // Only conclude the test once we receive both entries!
+      if (observedMark && observedMeasure) {
+        observer.disconnect();
+        t.done();
+      }
+    })
+  );
+  observer.observe({type: "mark"});
+  observer.observe({type: "measure"});
+  self.performance.mark("mark1");
+  self.performance.measure("measure1");
+}, "observe() with different type values stacks.");
diff --git a/test/fixtures/wpt/performance-timeline/po-observe.any.js b/test/fixtures/wpt/performance-timeline/po-observe.any.js
new file mode 100644
index 00000000000000..5b593374baf157
--- /dev/null
+++ b/test/fixtures/wpt/performance-timeline/po-observe.any.js
@@ -0,0 +1,63 @@
+// META: script=performanceobservers.js
+
+  test(function () {
+    const obs = new PerformanceObserver(() => {});
+    assert_throws_js(TypeError, function () {
+      obs.observe({entryTypes: "mark"});
+    });
+  }, "entryTypes must be a sequence or throw a TypeError");
+
+  test(function () {
+    const obs = new PerformanceObserver(() => {});
+    obs.observe({entryTypes: []});
+  }, "Empty sequence entryTypes does not throw an exception.");
+
+  test(function () {
+    const obs = new PerformanceObserver(() => {});
+    obs.observe({entryTypes: ["this-cannot-match-an-entryType"]});
+    obs.observe({entryTypes: ["marks","navigate", "resources"]});
+  }, "Unknown entryTypes do not throw an exception.");
+
+  test(function () {
+    const obs = new PerformanceObserver(() => {});
+    obs.observe({entryTypes: ["mark","this-cannot-match-an-entryType"]});
+    obs.observe({entryTypes: ["this-cannot-match-an-entryType","mark"]});
+    obs.observe({entryTypes: ["mark"], others: true});
+  }, "Filter unsupported entryType entryType names within the entryTypes sequence");
+
+  async_test(function (t) {
+    var finish = t.step_func(function () { t.done(); });
+    var observer = new PerformanceObserver(
+      function (entryList, obs) {
+        var self = this;
+        t.step(function () {
+          assert_true(entryList instanceof PerformanceObserverEntryList, "first callback parameter must be a PerformanceObserverEntryList instance");
+          assert_true(obs instanceof PerformanceObserver, "second callback parameter must be a PerformanceObserver instance");
+          assert_equals(observer, self, "observer is the this value");
+          assert_equals(observer, obs, "observer is second parameter");
+          assert_equals(self, obs, "this and second parameter are the same");
+          observer.disconnect();
+          finish();
+        });
+      }
+    );
+    self.performance.clearMarks();
+    observer.observe({entryTypes: ["mark"]});
+    self.performance.mark("mark1");
+  }, "Check observer callback parameter and this values");
+
+  async_test(function (t) {
+  var observer = new PerformanceObserver(
+      t.step_func(function (entryList, obs) {
+        checkEntries(entryList.getEntries(),
+          [{ entryType: "measure", name: "measure1"}]);
+        observer.disconnect();
+        t.done();
+      })
+    );
+    self.performance.clearMarks();
+    observer.observe({entryTypes: ["mark"]});
+    observer.observe({entryTypes: ["measure"]});
+    self.performance.mark("mark1");
+    self.performance.measure("measure1");
+  }, "replace observer if already present");
diff --git a/test/fixtures/wpt/performance-timeline/po-observe.html b/test/fixtures/wpt/performance-timeline/po-observe.html
new file mode 100644
index 00000000000000..a48f0f3764bda4
--- /dev/null
+++ b/test/fixtures/wpt/performance-timeline/po-observe.html
@@ -0,0 +1,86 @@
+<!DOCTYPE HTML>
+<meta charset=utf-8>
+<title>PerformanceObservers: PerformanceObserverInit.buffered</title>
+<meta name="timeout" content="long">
+<script src="/resources/testharness.js"></script>
+<script src="/resources/testharnessreport.js"></script>
+<script src="performanceobservers.js"></script>
+<h1>PerformanceObservers: PerformanceObserverInit.buffered</h1>
+<p>
+PerformanceObserverInit.buffered should retrieve previously buffered entries
+</p>
+<div id="log"></div>
+<script>
+  async_test(function (t) {
+    function initTest() {
+      new PerformanceObserver(function (entryList, observer) {
+        entryList.getEntries().forEach(function(entry) {
+          if (shouldExclude(entry)) {
+            return;
+          }
+
+          observedEntries.push(entry);
+          if (observedEntries.length === entryTypes.length) {
+            observer.disconnect();
+            runTest();
+          }
+        });
+      }).observe({entryTypes});
+
+      // creates a `resource` entry
+      var img = document.createElement("img");
+      img.src = "./resources/square.png";
+      document.body.appendChild(img);
+
+      performance.mark("markName"); // creates a `mark` entry
+      performance.measure("measureName"); // creates a `measure` entry
+    }
+    function shouldExclude(entry) {
+      // exclude all `resource` entries that aren't for "square.png"
+      return entry.entryType === "resource" &&
+             entry.name.indexOf("square.png") === -1;
+    }
+    function runTest() {
+      // this PerformanceObserver is a nop because we've already been notified about all of our `entryTypes`
+      var po_nop = new PerformanceObserver(function (entryList, observer) {
+        if (entryList.getEntries().find(function(entry) {
+          return !shouldExclude(entry);
+        })) {
+          assert_unreached("this PerformanceObserver callback should never be called");
+        }
+      });
+      po_nop.observe({
+        entryTypes,
+      });
+
+      // this PerformanceObserver should be notified about the previously
+      // buffered mark entry only
+      const bufferedEntries = [];
+      new PerformanceObserver(function (entryList, observer) {
+        entryList.getEntries().forEach(function(entry) {
+          if (shouldExclude(entry)) {
+            return;
+          }
+
+          bufferedEntries.push(entry);
+          if (bufferedEntries.length === 1) {
+            observer.disconnect();
+            po_nop.disconnect();
+            for (i = 0; i < bufferedEntries.length; i++) {
+              assert_equals(bufferedEntries[i].entryType, "mark")
+            }
+            t.done();
+          }
+        });
+      }).observe({
+        type: "mark",
+        buffered: true
+      });
+    }
+
+    const entryTypes = ["navigation", "resource", "mark", "measure"];
+    const observedEntries = [];
+    initTest();
+  }, "PerformanceObserverInit.buffered should retrieve previously buffered entries");
+
+</script>
diff --git a/test/fixtures/wpt/performance-timeline/po-resource.html b/test/fixtures/wpt/performance-timeline/po-resource.html
new file mode 100644
index 00000000000000..00c173eeae921f
--- /dev/null
+++ b/test/fixtures/wpt/performance-timeline/po-resource.html
@@ -0,0 +1,48 @@
+<!DOCTYPE HTML>
+<meta charset=utf-8>
+<title>PerformanceObservers: resource</title>
+<script src="/resources/testharness.js"></script>
+<script src="/resources/testharnessreport.js"></script>
+<script src="performanceobservers.js"></script>
+<h1>PerformanceObservers: resource</h1>
+<p>
+New resources will <a href="https://w3c.github.io/performance-timeline/#dfn-queue-a-performanceentry">queue a PerformanceEntry</a>.
+</p>
+<div id="log"></div>
+<script>
+  async_test(function (t) {
+    function path(pathname) {
+      var filename = pathname.substring(pathname.lastIndexOf('/')+1);
+      return pathname.substring(0, pathname.length - filename.length);
+    }
+    var gUniqueCounter = 0;
+    function generateUniqueValues() {
+      return Date.now() + "-" + (++gUniqueCounter);
+    }
+    var stored_entries = [];
+    var img_location = document.location.origin + path(document.location.pathname)
+       + "resources/square.png?random=";
+    var img1 = img_location + generateUniqueValues();
+    var img2 = img_location + generateUniqueValues();
+    var observer = new PerformanceObserver(
+        t.step_func(function (entryList, obs) {
+          stored_entries =
+            stored_entries.concat(entryList.getEntriesByType("resource"));
+          if (stored_entries.length >= 2) {
+            checkEntries(stored_entries,
+              [{ entryType: "resource", name: img1},
+               { entryType: "resource", name: img2}]);
+            observer.disconnect();
+            t.done();
+          }
+        })
+      );
+    observer.observe({entryTypes: ["resource"]});
+    var img = document.createElement("img");
+    img.src = img1;
+    document.body.appendChild(img);
+    img = document.createElement("img");
+    img.src = img2;
+    document.body.appendChild(img);
+  }, "resource entries are observable");
+</script>
diff --git a/test/fixtures/wpt/performance-timeline/po-takeRecords.any.js b/test/fixtures/wpt/performance-timeline/po-takeRecords.any.js
new file mode 100644
index 00000000000000..86ad397b0a5c37
--- /dev/null
+++ b/test/fixtures/wpt/performance-timeline/po-takeRecords.any.js
@@ -0,0 +1,34 @@
+// META: title=PerformanceObserver: takeRecords
+// META: script=performanceobservers.js
+
+async_test(function (t) {
+    const observer = new PerformanceObserver(function (entryList, observer) {
+      assert_unreached('This callback should not have been called.')
+    });
+    let entries = observer.takeRecords();
+    checkEntries(entries, [], 'No records before observe');
+    observer.observe({entryTypes: ['mark']});
+    assert_equals(typeof(observer.takeRecords), 'function');
+    entries = observer.takeRecords();
+    checkEntries(entries, [], 'No records just from observe');
+    performance.mark('a');
+    performance.mark('b');
+    entries = observer.takeRecords();
+    checkEntries(entries, [
+      {entryType: 'mark', name: 'a'},
+      {entryType: 'mark', name: 'b'}
+    ]);
+    performance.mark('c');
+    performance.mark('d');
+    performance.mark('e');
+    entries = observer.takeRecords();
+    checkEntries(entries, [
+      {entryType: 'mark', name: 'c'},
+      {entryType: 'mark', name: 'd'},
+      {entryType: 'mark', name: 'e'}
+    ]);
+    entries = observer.takeRecords();
+    checkEntries(entries, [], 'No entries right after takeRecords');
+    observer.disconnect();
+    t.done();
+  }, "Test PerformanceObserver's takeRecords()");
diff --git a/test/fixtures/wpt/performance-timeline/resources/postmessage-entry.html b/test/fixtures/wpt/performance-timeline/resources/postmessage-entry.html
new file mode 100644
index 00000000000000..ef5be73395b49d
--- /dev/null
+++ b/test/fixtures/wpt/performance-timeline/resources/postmessage-entry.html
@@ -0,0 +1,17 @@
+<!doctype html>
+<script>
+addEventListener("load", () => {
+  const entry = performance.getEntriesByType("navigation")[0];
+  try {
+    window.top.postMessage(entry, "*");
+  } catch(error) {
+    if (error.name == "DataCloneError") {
+      window.top.postMessage("PASS", "*");
+    } else {
+      window.top.postMessage("FAIL - Wrong exception name: " + error.name, "*");
+    }
+  }
+  window.top.postMessage("FAIL - No exception thrown", "*");
+});
+
+</script>
diff --git a/test/fixtures/wpt/performance-timeline/resources/square.png b/test/fixtures/wpt/performance-timeline/resources/square.png
new file mode 100644
index 00000000000000..be211bc3771803
Binary files /dev/null and b/test/fixtures/wpt/performance-timeline/resources/square.png differ
diff --git a/test/fixtures/wpt/performance-timeline/resources/worker-invalid-entries.js b/test/fixtures/wpt/performance-timeline/resources/worker-invalid-entries.js
new file mode 100644
index 00000000000000..bd7fba2ccf4b6a
--- /dev/null
+++ b/test/fixtures/wpt/performance-timeline/resources/worker-invalid-entries.js
@@ -0,0 +1,6 @@
+performance.mark('workerMark');
+postMessage({
+  'invalid' : performance.getEntriesByType('invalid').length,
+  'mark' : performance.getEntriesByType('mark').length,
+  'measure' : performance.getEntriesByType('measure').length
+});
diff --git a/test/fixtures/wpt/performance-timeline/resources/worker-with-performance-observer.js b/test/fixtures/wpt/performance-timeline/resources/worker-with-performance-observer.js
new file mode 100644
index 00000000000000..a72fe81c47feac
--- /dev/null
+++ b/test/fixtures/wpt/performance-timeline/resources/worker-with-performance-observer.js
@@ -0,0 +1,6 @@
+try {
+  new PerformanceObserver(() => true);
+  postMessage("SUCCESS");
+} catch (ex) {
+  postMessage("FAILURE");
+}
diff --git a/test/fixtures/wpt/performance-timeline/supportedEntryTypes.any.js b/test/fixtures/wpt/performance-timeline/supportedEntryTypes.any.js
new file mode 100644
index 00000000000000..25f195939e7b69
--- /dev/null
+++ b/test/fixtures/wpt/performance-timeline/supportedEntryTypes.any.js
@@ -0,0 +1,19 @@
+test(() => {
+  if (typeof PerformanceObserver.supportedEntryTypes === "undefined")
+    assert_unreached("supportedEntryTypes is not supported.");
+  const types = PerformanceObserver.supportedEntryTypes;
+  assert_greater_than(types.length, 0,
+    "There should be at least one entry in supportedEntryTypes.");
+  for (let i = 1; i < types.length; i++) {
+    assert_true(types[i-1] < types[i],
+      "The strings '" + types[i-1] + "' and '" + types[i] +
+      "' are repeated or they are not in alphabetical order.")
+  }
+}, "supportedEntryTypes exists and returns entries in alphabetical order");
+
+test(() => {
+  if (typeof PerformanceObserver.supportedEntryTypes === "undefined")
+    assert_unreached("supportedEntryTypes is not supported.");
+  assert_true(PerformanceObserver.supportedEntryTypes ===
+      PerformanceObserver.supportedEntryTypes);
+}, "supportedEntryTypes caches result");
diff --git a/test/fixtures/wpt/performance-timeline/webtiming-resolution.any.js b/test/fixtures/wpt/performance-timeline/webtiming-resolution.any.js
new file mode 100644
index 00000000000000..d869c7c52d55d6
--- /dev/null
+++ b/test/fixtures/wpt/performance-timeline/webtiming-resolution.any.js
@@ -0,0 +1,25 @@
+function testTimeResolution(highResTimeFunc, funcString) {
+    test(() => {
+        const t0 = highResTimeFunc();
+        let t1 = highResTimeFunc();
+        while (t0 == t1) {
+            t1 = highResTimeFunc();
+        }
+        const epsilon = 1e-5;
+        assert_greater_than_equal(t1 - t0, 0.005 - epsilon, 'The second ' + funcString + ' should be much greater than the first');
+    }, 'Verifies the resolution of ' + funcString + ' is at least 5 microseconds.');
+}
+
+function timeByPerformanceNow() {
+    return performance.now();
+}
+
+function timeByUserTiming() {
+    performance.mark('timer');
+    const time = performance.getEntriesByName('timer')[0].startTime;
+    performance.clearMarks('timer');
+    return time;
+}
+
+testTimeResolution(timeByPerformanceNow, 'performance.now()');
+testTimeResolution(timeByUserTiming, 'entry.startTime');
diff --git a/test/fixtures/wpt/performance-timeline/worker-with-performance-observer.html b/test/fixtures/wpt/performance-timeline/worker-with-performance-observer.html
new file mode 100644
index 00000000000000..fc92bc971003f2
--- /dev/null
+++ b/test/fixtures/wpt/performance-timeline/worker-with-performance-observer.html
@@ -0,0 +1,18 @@
+<!doctype html>
+<html>
+<head>
+<script src="/resources/testharness.js"></script>
+<script src="/resources/testharnessreport.js"></script>
+</head>
+<body>
+<script>
+async_test(function(t) {
+  const worker = new Worker("resources/worker-with-performance-observer.js");
+  worker.onmessage = function(event) {
+    t.step(() => assert_equals(event.data, 'SUCCESS'));
+    t.done();
+  }
+}, 'Worker: Test Performance Observer inside a worker.');
+</script>
+</body>
+</html>
diff --git a/test/fixtures/wpt/user-timing/META.yml b/test/fixtures/wpt/user-timing/META.yml
new file mode 100644
index 00000000000000..5cb2a789c09c89
--- /dev/null
+++ b/test/fixtures/wpt/user-timing/META.yml
@@ -0,0 +1,4 @@
+spec: https://w3c.github.io/user-timing/
+suggested_reviewers:
+  - plehegar
+  - igrigorik
diff --git a/test/fixtures/wpt/user-timing/buffered-flag.any.js b/test/fixtures/wpt/user-timing/buffered-flag.any.js
new file mode 100644
index 00000000000000..f938c8522d829a
--- /dev/null
+++ b/test/fixtures/wpt/user-timing/buffered-flag.any.js
@@ -0,0 +1,27 @@
+async_test(t => {
+  // First observer creates second in callback to ensure the entry has been dispatched by the time
+  // the second observer begins observing.
+  new PerformanceObserver(() => {
+    // Second observer requires 'buffered: true' to see an entry.
+    new PerformanceObserver(t.step_func_done(list => {
+      const entries = list.getEntries();
+      assert_equals(entries.length, 1, 'There should be 1 mark entry.');
+      assert_equals(entries[0].entryType, 'mark');
+    })).observe({type: 'mark', buffered: true});
+  }).observe({entryTypes: ['mark']});
+  performance.mark('foo');
+}, 'PerformanceObserver with buffered flag sees previous marks');
+
+async_test(t => {
+  // First observer creates second in callback to ensure the entry has been dispatched by the time
+  // the second observer begins observing.
+  new PerformanceObserver(() => {
+    // Second observer requires 'buffered: true' to see an entry.
+    new PerformanceObserver(t.step_func_done(list => {
+      const entries = list.getEntries();
+      assert_equals(entries.length, 1, 'There should be 1 measure entry.');
+      assert_equals(entries[0].entryType, 'measure');
+    })).observe({type: 'measure', buffered: true});
+  }).observe({entryTypes: ['measure']});
+  performance.measure('bar');
+}, 'PerformanceObserver with buffered flag sees previous measures');
diff --git a/test/fixtures/wpt/user-timing/case-sensitivity.any.js b/test/fixtures/wpt/user-timing/case-sensitivity.any.js
new file mode 100644
index 00000000000000..1c0b0dcac361fe
--- /dev/null
+++ b/test/fixtures/wpt/user-timing/case-sensitivity.any.js
@@ -0,0 +1,25 @@
+  test(function () {
+    assert_equals(typeof self.performance, "object");
+    assert_equals(typeof self.performance.getEntriesByType, "function");
+
+    self.performance.mark("mark1");
+    self.performance.measure("measure1");
+
+    const type = [
+      'mark',
+      'measure',
+    ];
+    type.forEach(function(entryType) {
+      if (PerformanceObserver.supportedEntryTypes.includes(entryType)) {
+        const entryTypeUpperCased = entryType.toUpperCase();
+        const entryTypeCapitalized = entryType[0].toUpperCase() + entryType.substring(1);
+        const lowerList = self.performance.getEntriesByType(entryType);
+        const upperList = self.performance.getEntriesByType(entryTypeUpperCased);
+        const mixedList = self.performance.getEntriesByType(entryTypeCapitalized);
+
+        assert_greater_than(lowerList.length, 0, "Entries exist");
+        assert_equals(upperList.length, 0, "getEntriesByType('" + entryTypeCapitalized + "').length");
+        assert_equals(mixedList.length, 0, "getEntriesByType('" + entryTypeCapitalized + "').length");
+      }
+    });
+  }, "getEntriesByType values are case sensitive");
diff --git a/test/fixtures/wpt/user-timing/clearMarks.html b/test/fixtures/wpt/user-timing/clearMarks.html
new file mode 100644
index 00000000000000..92c60a3bbb856b
--- /dev/null
+++ b/test/fixtures/wpt/user-timing/clearMarks.html
@@ -0,0 +1,84 @@
+<!DOCTYPE html>
+<html>
+<head>
+<meta charset="utf-8" />
+<title>functionality test of window.performance.clearMarks</title>
+<link rel="author" title="Intel" href="http://www.intel.com/" />
+<link rel="help" href="http://www.w3.org/TR/user-timing/#extensions-performance-interface"/>
+<script src="/resources/testharness.js"></script>
+<script src="/resources/testharnessreport.js"></script>
+<script src="/common/performance-timeline-utils.js"></script>
+<script src="resources/webperftestharness.js"></script>
+<script src="resources/webperftestharnessextension.js"></script>
+<script>
+setup({ explicit_done: true });
+
+function onload_test()
+{
+    const entrylist_checker = new performance_entrylist_checker('mark');
+    const string_mark_names = mark_names.map(function (x) { return String(x)});
+    mark_names.forEach(function(name) {
+        performance.mark(name);
+    });
+
+    for (let i = 0; i < mark_names.length; ++i)
+    {
+        performance.clearMarks(mark_names[i]);
+        const retained_entries = performance.getEntriesByType('mark');
+        const non_retained_entries = performance.getEntriesByName(mark_names[i], 'mark');
+        entrylist_checker.entrylist_check(retained_entries, mark_names.length - i - 1, string_mark_names,
+            'First loop: checking entries after removing "' + mark_names[i] + '". ');
+        test_equals(non_retained_entries.length, 0,
+            'First loop: marks that we cleared for "' + mark_names[i] + '" should not exist anymore.');
+    }
+
+    mark_names.forEach(function(name) {
+        performance.mark(name);
+    });
+    performance.clearMarks();
+    test_equals(performance.getEntriesByType('mark').length, 0, 'No marks should exist after we clear all.');
+
+    // Following cases test clear existed mark name that is tied for two times.
+    mark_names.forEach(function(name) {
+        performance.mark(name);
+    });
+    mark_names.forEach(function(name) {
+        performance.mark(name);
+    });
+
+    for (let i = 0; i < mark_names.length; ++i)
+    {
+        performance.clearMarks(mark_names[i]);
+        const retained_entries = performance.getEntriesByType('mark');
+        const non_retained_entries = performance.getEntriesByName(mark_names[i], 'mark');
+        entrylist_checker.entrylist_check(retained_entries, (mark_names.length - i - 1) * 2, string_mark_names,
+            'Second loop: checking entries after removing "' + mark_names[i] + '". ');
+        test_equals(non_retained_entries.length, 0,
+            'Second loop: marks that we cleared for "' + mark_names[i] + '" should not exist anymore.');
+    }
+
+    // Following cases test clear functionality when mark names are tied for two times.
+    mark_names.forEach(function(name) {
+        performance.mark(name);
+    });
+    mark_names.forEach(function(name) {
+        performance.mark(name);
+    });
+    var entry_number_before_useless_clear = performance.getEntriesByType('Mark').length;
+    performance.clearMarks('NonExist');
+    var entry_number_after_useless_clear = performance.getEntriesByType('Mark').length;
+    test_equals(entry_number_before_useless_clear, entry_number_after_useless_clear, 'Nothing should happen if we clear a non-exist mark.');
+
+    performance.clearMarks();
+    test_equals(performance.getEntriesByType('mark').length, 0, 'No marks should exist when we clear all.');
+
+    done();
+}
+</script>
+</head>
+<body onload=onload_test()>
+    <h1>Description</h1>
+    <p>This test validates functionality of the interface window.performance.clearMarks.</p>
+    <div id="log"></div>
+</body>
+</html>
diff --git a/test/fixtures/wpt/user-timing/clearMeasures.html b/test/fixtures/wpt/user-timing/clearMeasures.html
new file mode 100644
index 00000000000000..54d41005698305
--- /dev/null
+++ b/test/fixtures/wpt/user-timing/clearMeasures.html
@@ -0,0 +1,77 @@
+<!DOCTYPE html>
+<html>
+<head>
+<meta charset="utf-8" />
+<title>functionality test of window.performance.clearMeasures</title>
+<link rel="author" title="Intel" href="http://www.intel.com/" />
+<link rel="help" href="http://www.w3.org/TR/user-timing/#extensions-performance-interface"/>
+<script src="/resources/testharness.js"></script>
+<script src="/resources/testharnessreport.js"></script>
+<script src="/common/performance-timeline-utils.js"></script>
+<script src="resources/webperftestharness.js"></script>
+<script src="resources/webperftestharnessextension.js"></script>
+<script>
+setup({ explicit_done: true });
+
+function onload_test()
+{
+    const context = new PerformanceContext(window.performance);
+    const entrylist_checker = new performance_entrylist_checker('measure');
+    const measure_names = measures.map(function(x) {return x[0];});
+
+    mark_names.forEach(function(name) {
+        context.mark(name);
+    });
+    measures.forEach(context.initialMeasures, context);
+    for (let i = 0; i < measures.length; ++i)
+    {
+        context.clearMeasures(measures[i][0]);
+        const retained_entries = context.getEntriesByType('measure');
+        const non_retained_entries = context.getEntriesByName(measures[i][0], 'measure');
+        entrylist_checker.entrylist_check(retained_entries, measures.length - i - 1, measure_names,
+            'First loop: checking entries after removing "' + measures[i][0] + '". ');
+        test_equals(non_retained_entries.length, 0,
+            'First loop: measure "' + measures[i][0] + '" should not exist anymore after we cleared it.');
+    }
+
+    measures.forEach(context.initialMeasures, context);
+    context.clearMeasures();
+    test_equals(context.getEntriesByType('measure').length, 0, 'No measures should exist after we clear all (after first loop).');
+
+    // Following cases test clear existed measure name that is tied twice.
+    measures.forEach(context.initialMeasures, context);
+    mark_names.forEach(function(name) {
+        context.mark(name);
+    });
+    measures.forEach(context.initialMeasures, context);
+    for (let i = 0; i < measures.length; ++i)
+    {
+        context.clearMeasures(measures[i][0]);
+        const retained_entries = context.getEntriesByType('measure');
+        const non_retained_entries = context.getEntriesByName(measures[i][0], 'measure');
+        entrylist_checker.entrylist_check(retained_entries, (measures.length - i - 1) * 2, measure_names,
+            'Second loop: checking entries after removing "' + measures[i][0] + '". ');
+        test_equals(non_retained_entries.length, 0,
+            'Second loop: measure "' + measures[i][0] +'" should not exist anymore after we cleared it.');
+    }
+
+    // Following cases test clear functionality when measure names are tied twice.
+    measures.forEach(context.initialMeasures, context);
+    measures.forEach(context.initialMeasures, context);
+    const entry_number_before_useless_clear = context.getEntriesByType('measure').length;
+    context.clearMeasures('NonExist');
+    const entry_number_after_useless_clear = context.getEntriesByType('measure').length;
+    test_equals(entry_number_before_useless_clear, entry_number_after_useless_clear, 'Nothing should happen if we clear a non-exist measure');
+    context.clearMeasures();
+    test_equals(context.getEntriesByType('measure').length, 0, 'No measures should exist when we clear all (after second loop).');
+
+    done();
+}
+</script>
+</head>
+<body onload=onload_test()>
+    <h1>Description</h1>
+    <p>This test validates functionality of the interface window.performance.clearMeasures.</p>
+    <div id="log"></div>
+</body>
+</html>
diff --git a/test/fixtures/wpt/user-timing/clear_all_marks.any.js b/test/fixtures/wpt/user-timing/clear_all_marks.any.js
new file mode 100644
index 00000000000000..35cd2a04f61036
--- /dev/null
+++ b/test/fixtures/wpt/user-timing/clear_all_marks.any.js
@@ -0,0 +1,17 @@
+test(function() {
+    self.performance.mark("mark1");
+    self.performance.mark("mark2");
+
+    // test that two marks have been created
+    var entries = self.performance.getEntriesByType("mark");
+    assert_equals(entries.length, 2, "Two marks have been created for this test.");
+
+    // clear all marks
+    self.performance.clearMarks();
+
+    // test that all marks were cleared
+    entries = self.performance.getEntriesByType("mark");
+
+    assert_equals(entries.length, 0, "All marks have been cleared.");
+
+}, "Clearing all marks remove all of them.");
diff --git a/test/fixtures/wpt/user-timing/clear_all_measures.any.js b/test/fixtures/wpt/user-timing/clear_all_measures.any.js
new file mode 100644
index 00000000000000..32c993f2827a30
--- /dev/null
+++ b/test/fixtures/wpt/user-timing/clear_all_measures.any.js
@@ -0,0 +1,21 @@
+test(function()
+{
+    self.performance.mark("mark1");
+    self.performance.measure("measure1", "mark1");
+    self.performance.mark("mark2");
+    self.performance.measure("measure2", "mark2");
+
+    // test that two measures have been created
+    var entries = self.performance.getEntriesByType("measure");
+    assert_equals(entries.length, 2, "Two measures have been created for this test.");
+
+    // clear all measures
+    self.performance.clearMeasures();
+
+    // test that all measures were cleared
+    entries = self.performance.getEntriesByType("measure");
+    assert_equals(entries.length, 0,
+              "After a call to self.performance.clearMeasures(), " +
+              "self.performance.getEntriesByType(\"measure\") returns an empty object.");
+
+}, "Clearing all marks remove all of them.");
diff --git a/test/fixtures/wpt/user-timing/clear_non_existent_mark.any.js b/test/fixtures/wpt/user-timing/clear_non_existent_mark.any.js
new file mode 100644
index 00000000000000..c7d8b478613401
--- /dev/null
+++ b/test/fixtures/wpt/user-timing/clear_non_existent_mark.any.js
@@ -0,0 +1,26 @@
+test(function() {
+    self.performance.mark("mark1");
+    self.performance.mark("mark2");
+
+    // test that two marks have been created
+    var entries = self.performance.getEntriesByType("mark");
+    assert_equals(entries.length, 2, "Two marks have been created for this test.");
+
+    // clear non-existent mark
+    self.performance.clearMarks("mark3");
+
+    // test that "mark1" still exists
+    entries = self.performance.getEntriesByName("mark1");
+    assert_equals(entries[0].name, "mark1",
+              "After a call to self.performance.clearMarks(\"mark3\"), where \"mark3" +
+              "\" is a non-existent mark, self.performance.getEntriesByName(\"mark1\") " +
+              "returns an object containing the \"mark1\" mark.");
+
+    // test that "mark2" still exists
+    entries = self.performance.getEntriesByName("mark2");
+    assert_equals(entries[0].name, "mark2",
+              "After a call to self.performance.clearMarks(\"mark3\"), where \"mark3" +
+              "\" is a non-existent mark, self.performance.getEntriesByName(\"mark2\") " +
+              "returns an object containing the \"mark2\" mark.");
+
+}, "Clearing a non-existent mark doesn't affect existing marks");
diff --git a/test/fixtures/wpt/user-timing/clear_non_existent_measure.any.js b/test/fixtures/wpt/user-timing/clear_non_existent_measure.any.js
new file mode 100644
index 00000000000000..9de0b5f266d4e2
--- /dev/null
+++ b/test/fixtures/wpt/user-timing/clear_non_existent_measure.any.js
@@ -0,0 +1,29 @@
+test(function()
+{
+    self.performance.mark("mark1");
+    self.performance.measure("measure1", "mark1");
+    self.performance.mark("mark2");
+    self.performance.measure("measure2", "mark2");
+
+    // test that two measures have been created
+    var entries = self.performance.getEntriesByType("measure");
+    assert_equals(entries.length, 2, "Two measures have been created for this test.");
+
+    // clear non-existent measure
+    self.performance.clearMeasures("measure3");
+
+    // test that "measure1" still exists
+    entries = self.performance.getEntriesByName("measure1");
+    assert_equals(entries[0].name, "measure1",
+              "After a call to self.performance.clearMeasures(\"measure3\"), where \"measure3" +
+              "\" is a non-existent measure, self.performance.getEntriesByName(\"measure1\") " +
+              "returns an object containing the \"measure1\" measure.");
+
+    // test that "measure2" still exists
+    entries = self.performance.getEntriesByName("measure2");
+    assert_equals(entries[0].name, "measure2",
+              "After a call to self.performance.clearMeasures(\"measure3\"), where \"measure3" +
+              "\" is a non-existent measure, self.performance.getEntriesByName(\"measure2\") " +
+              "returns an object containing the \"measure2\" measure.");
+
+}, "Clearing a non-existent measure doesn't affect existing measures");
diff --git a/test/fixtures/wpt/user-timing/clear_one_mark.any.js b/test/fixtures/wpt/user-timing/clear_one_mark.any.js
new file mode 100644
index 00000000000000..c180199d8c9f92
--- /dev/null
+++ b/test/fixtures/wpt/user-timing/clear_one_mark.any.js
@@ -0,0 +1,26 @@
+test(function() {
+    self.performance.mark("mark1");
+    self.performance.mark("mark2");
+
+    // test that two marks have been created
+    var entries = self.performance.getEntriesByType("mark");
+    assert_equals(entries.length, 2, "Two marks have been created for this test.");
+
+    // clear existent mark
+    self.performance.clearMarks("mark1");
+
+    // test that "mark1" was cleared
+    entries = self.performance.getEntriesByName("mark1");
+
+    assert_equals(entries.length, 0,
+              "After a call to self.performance.clearMarks(\"mark1\"), " +
+              "window.performance.getEntriesByName(\"mark1\") returns an empty object.");
+
+    // test that "mark2" still exists
+    entries = self.performance.getEntriesByName("mark2");
+    assert_equals(entries[0].name, "mark2",
+              "After a call to self.performance.clearMarks(\"mark1\"), " +
+              "window.performance.getEntriesByName(\"mark2\") returns an object containing the " +
+              "\"mark2\" mark.");
+
+}, "Clearing an existent mark doesn't affect other existing marks");
diff --git a/test/fixtures/wpt/user-timing/clear_one_measure.any.js b/test/fixtures/wpt/user-timing/clear_one_measure.any.js
new file mode 100644
index 00000000000000..a5e663772c8bbe
--- /dev/null
+++ b/test/fixtures/wpt/user-timing/clear_one_measure.any.js
@@ -0,0 +1,29 @@
+test(function()
+{
+    self.performance.mark("mark1");
+    self.performance.measure("measure1", "mark1");
+    self.performance.mark("mark2");
+    self.performance.measure("measure2", "mark2");
+
+    // test that two measures have been created
+    var entries = self.performance.getEntriesByType("measure");
+    assert_equals(entries.length, 2, "Two measures have been created for this test.");
+
+    // clear existent measure
+    self.performance.clearMeasures("measure1");
+
+    // test that "measure1" was cleared
+    entries = self.performance.getEntriesByName("measure1");
+
+    assert_equals(entries.length, 0,
+              "After a call to self.performance.clearMeasures(\"measure1\"), " +
+              "self.performance.getEntriesByName(\"measure1\") returns an empty object.");
+
+    // test that "measure2" still exists
+    entries = self.performance.getEntriesByName("measure2");
+    assert_equals(entries[0].name, "measure2",
+              "After a call to self.performance.clearMeasures(\"measure1\"), " +
+              "self.performance.getEntriesByName(\"measure2\") returns an object containing the " +
+              "\"measure2\" measure.");
+
+}, "Clearing an existent measure doesn't affect other existing measures");
diff --git a/test/fixtures/wpt/user-timing/entry_type.any.js b/test/fixtures/wpt/user-timing/entry_type.any.js
new file mode 100644
index 00000000000000..1e37453d09d42e
--- /dev/null
+++ b/test/fixtures/wpt/user-timing/entry_type.any.js
@@ -0,0 +1,13 @@
+test(function () {
+  self.performance.mark('mark');
+  var mark_entry = self.performance.getEntriesByName('mark')[0];
+
+  assert_equals(Object.prototype.toString.call(mark_entry), '[object PerformanceMark]', 'Class name of mark entry should be PerformanceMark.');
+}, "Validate the user timing entry type PerformanceMark");
+
+test(function () {
+  self.performance.measure('measure');
+  var measure_entry = self.performance.getEntriesByName('measure')[0];
+
+  assert_equals(Object.prototype.toString.call(measure_entry), '[object PerformanceMeasure]', 'Class name of measure entry should be PerformanceMeasure.');
+}, "Validate the user timing entry type PerformanceMeasure");
diff --git a/test/fixtures/wpt/user-timing/idlharness.any.js b/test/fixtures/wpt/user-timing/idlharness.any.js
new file mode 100644
index 00000000000000..511f2d0455b833
--- /dev/null
+++ b/test/fixtures/wpt/user-timing/idlharness.any.js
@@ -0,0 +1,33 @@
+// META: global=window,worker
+// META: script=/resources/WebIDLParser.js
+// META: script=/resources/idlharness.js
+// META: timeout=long
+
+// https://w3c.github.io/user-timing/
+
+'use strict';
+
+idl_test(
+  ['user-timing'],
+  ['hr-time', 'performance-timeline', 'dom'],
+  idl_array => {
+    try {
+      performance.mark('test');
+      performance.measure('test');
+      for (const m of performance.getEntriesByType('mark')) {
+        self.mark = m;
+      }
+      for (const m of performance.getEntriesByType('measure')) {
+        self.measure = m;
+      }
+    } catch (e) {
+      // Will be surfaced when mark is undefined below.
+    }
+
+    idl_array.add_objects({
+      Performance: ['performance'],
+      PerformanceMark: ['mark'],
+      PerformanceMeasure: ['measure'],
+    });
+  }
+);
diff --git a/test/fixtures/wpt/user-timing/invoke_with_timing_attributes.html b/test/fixtures/wpt/user-timing/invoke_with_timing_attributes.html
new file mode 100644
index 00000000000000..1df94a3006d7fb
--- /dev/null
+++ b/test/fixtures/wpt/user-timing/invoke_with_timing_attributes.html
@@ -0,0 +1,35 @@
+<!DOCTYPE html>
+<html>
+  <head>
+    <meta charset="utf-8" />
+    <title>exception test of performance.mark and performance.measure</title>
+    <meta rel="help" href="https://w3c.github.io/user-timing/#extensions-performance-interface"/>
+    <script src="/resources/testharness.js"></script>
+    <script src="/resources/testharnessreport.js"></script>
+    <script src="resources/webperftestharness.js"></script>
+  </head>
+  <body>
+    <h1>Description</h1>
+    <p>This test validates exception scenarios of invoking mark() and measure() with timing attributes as value.</p>
+    <div id="log"></div>
+    <script>
+function emit_test(attrName) {
+    test(function() {
+        assert_throws_dom("SyntaxError", function() { window.performance.mark(attrName); });
+    }, "performance.mark should throw if used with timing attribute " + attrName);
+}
+for (var i in timingAttributes) {
+  emit_test(timingAttributes[i]);
+}
+
+function emit_test2(attrName) {
+    test(function() {
+        window.performance.measure(attrName);
+    }, "performance.measure should not throw if used with timing attribute " + attrName);
+}
+for (var i in timingAttributes) {
+  emit_test2(timingAttributes[i]);
+}
+    </script>
+  </body>
+</html>
diff --git a/test/fixtures/wpt/user-timing/invoke_with_timing_attributes.worker.js b/test/fixtures/wpt/user-timing/invoke_with_timing_attributes.worker.js
new file mode 100644
index 00000000000000..32677c64d3bd5f
--- /dev/null
+++ b/test/fixtures/wpt/user-timing/invoke_with_timing_attributes.worker.js
@@ -0,0 +1,25 @@
+importScripts("/resources/testharness.js");
+importScripts("resources/webperftestharness.js");
+
+function emit_test(attrName) {
+    test(function() {
+      performance.mark(attrName);
+      performance.clearMarks(attrName);
+    }, "performance.mark should not throw if used with timing attribute " + attrName
+       + " in workers");
+}
+for (var i in timingAttributes) {
+  emit_test(timingAttributes[i]);
+}
+
+function emit_test2(attrName) {
+    test(function() {
+      performance.measure(attrName);
+      performance.clearMeasures(attrName);
+    }, "performance.measure should not throw if used with timing attribute " + attrName
+       + " in workers");
+}
+for (var i in timingAttributes) {
+  emit_test2(timingAttributes[i]);
+}
+done();
diff --git a/test/fixtures/wpt/user-timing/invoke_without_parameter.html b/test/fixtures/wpt/user-timing/invoke_without_parameter.html
new file mode 100644
index 00000000000000..114435e59befbb
--- /dev/null
+++ b/test/fixtures/wpt/user-timing/invoke_without_parameter.html
@@ -0,0 +1,26 @@
+<!DOCTYPE html>
+<html>
+    <head>
+        <meta charset="utf-8" />
+        <title>exception test of performance.mark and performance.measure</title>
+        <link rel="author" title="Intel" href="http://www.intel.com/" />
+        <link rel="help" href="https://w3c.github.io/user-timing/#extensions-performance-interface"/>
+        <script src="/resources/testharness.js"></script>
+        <script src="/resources/testharnessreport.js"></script>
+        <script src="resources/webperftestharness.js"></script>
+    </head>
+    <body>
+        <h1>Description</h1>
+        <p>This test validates exception scenarios of invoking mark() and measure() without parameter.</p>
+        <div id="log"></div>
+        <script>
+test(function () {
+    assert_throws_js(TypeError, function () { window.performance.mark() });
+}, "window.performance.mark() throws a TypeError exception when invoke without a parameter.");
+
+test(function () {
+    assert_throws_js(TypeError, function () { window.performance.measure(); });
+}, "window.performance.measure() throws a TypeError exception when invoke without a parameter.");
+        </script>
+    </body>
+</html>
diff --git a/test/fixtures/wpt/user-timing/mark-entry-constructor.any.js b/test/fixtures/wpt/user-timing/mark-entry-constructor.any.js
new file mode 100644
index 00000000000000..ef9c403dda6723
--- /dev/null
+++ b/test/fixtures/wpt/user-timing/mark-entry-constructor.any.js
@@ -0,0 +1,40 @@
+// META: script=resources/user-timing-helper.js
+
+test(()=>{
+  const entry = new PerformanceMark("name");
+  assert_true(entry instanceof PerformanceMark);
+  checkEntry(entry, {name: "name", entryType: "mark"});
+}, "Mark entry can be created by 'new PerformanceMark(string)'.");
+
+test(()=>{
+  const entry = new PerformanceMark("name", {});
+  assert_true(entry instanceof PerformanceMark);
+  checkEntry(entry, {name: "name", entryType: "mark"});
+}, "Mark entry can be created by 'new PerformanceMark(string, {})'.");
+
+test(()=>{
+  const entry = new PerformanceMark("name", {startTime: 1});
+  assert_true(entry instanceof PerformanceMark);
+  checkEntry(entry, {name: "name", entryType: "mark", startTime: 1});
+}, "Mark entry can be created by 'new PerformanceMark(string, {startTime})'.");
+
+test(()=>{
+  const entry = new PerformanceMark("name", {detail: {info: "abc"}});
+  assert_true(entry instanceof PerformanceMark);
+  checkEntry(entry, {name: "name", entryType: "mark", detail: {info: "abc"}});
+}, "Mark entry can be created by 'new PerformanceMark(string, {detail})'.");
+
+test(()=>{
+  const entry =
+      new PerformanceMark("name", {startTime: 1, detail: {info: "abc"}});
+  assert_true(entry instanceof PerformanceMark);
+  checkEntry(entry, {name: "name", entryType: "mark", startTime: 1, detail: {info: "abc"}});
+}, "Mark entry can be created by " +
+   "'new PerformanceMark(string, {startTime, detail})'.");
+
+test(()=>{
+  const entry = new PerformanceMark("name");
+  assert_true(entry instanceof PerformanceMark);
+  checkEntry(entry, {name: "name", entryType: "mark"});
+  assert_equals(performance.getEntriesByName("name").length, 0);
+}, "Using new PerformanceMark() shouldn't add the entry to performance timeline.");
diff --git a/test/fixtures/wpt/user-timing/mark-errors.any.js b/test/fixtures/wpt/user-timing/mark-errors.any.js
new file mode 100644
index 00000000000000..dcd36695e22f2c
--- /dev/null
+++ b/test/fixtures/wpt/user-timing/mark-errors.any.js
@@ -0,0 +1,15 @@
+test(function() {
+  assert_throws_js(TypeError, function() { self.performance.mark("mark1", 123); }, "Number passed as a dict argument should cause type-error.")
+}, "Number should be rejected as the mark-options.")
+
+test(function() {
+  assert_throws_js(TypeError, function() { self.performance.mark("mark1", NaN); }, "NaN passed as a dict argument should cause type-error.")
+}, "NaN should be rejected as the mark-options.")
+
+test(function() {
+  assert_throws_js(TypeError, function() { self.performance.mark("mark1", Infinity); }, "Infinity passed as a dict argument should cause type-error.")
+}, "Infinity should be rejected as the mark-options.")
+
+test(function() {
+  assert_throws_js(TypeError, function() { self.performance.mark("mark1", "string"); }, "String passed as a dict argument should cause type-error.")
+}, "String should be rejected as the mark-options.")
diff --git a/test/fixtures/wpt/user-timing/mark-l3.any.js b/test/fixtures/wpt/user-timing/mark-l3.any.js
new file mode 100644
index 00000000000000..407a5c8bba6a3c
--- /dev/null
+++ b/test/fixtures/wpt/user-timing/mark-l3.any.js
@@ -0,0 +1,39 @@
+// META: script=resources/user-timing-helper.js
+
+async_test(function (t) {
+    let mark_entries = [];
+    const expected_entries =
+        [{ entryType: "mark", name: "mark1", detail: null},
+        { entryType: "mark", name: "mark2", detail: null},
+        { entryType: "mark", name: "mark3", detail: null},
+        { entryType: "mark", name: "mark4", detail: null},
+        { entryType: "mark", name: "mark5", detail: null},
+        { entryType: "mark", name: "mark6", detail: {}},
+        { entryType: "mark", name: "mark7", detail: {info: 'abc'}},
+        { entryType: "mark", name: "mark8", detail: null, startTime: 234.56},
+        { entryType: "mark", name: "mark9", detail: {count: 3}, startTime: 345.67}];
+    const observer = new PerformanceObserver(
+        t.step_func(function (entryList, obs) {
+          mark_entries =
+            mark_entries.concat(entryList.getEntries());
+          if (mark_entries.length >= expected_entries.length) {
+            checkEntries(mark_entries, expected_entries);
+            observer.disconnect();
+            t.done();
+          }
+        })
+      );
+    self.performance.clearMarks();
+    observer.observe({entryTypes: ["mark"]});
+    const returned_entries = [];
+    returned_entries.push(self.performance.mark("mark1"));
+    returned_entries.push(self.performance.mark("mark2", undefined));
+    returned_entries.push(self.performance.mark("mark3", null));
+    returned_entries.push(self.performance.mark("mark4", {}));
+    returned_entries.push(self.performance.mark("mark5", {detail: null}));
+    returned_entries.push(self.performance.mark("mark6", {detail: {}}));
+    returned_entries.push(self.performance.mark("mark7", {detail: {info: 'abc'}}));
+    returned_entries.push(self.performance.mark("mark8", {startTime: 234.56}));
+    returned_entries.push(self.performance.mark("mark9", {detail: {count: 3}, startTime: 345.67}));
+    checkEntries(returned_entries, expected_entries);
+}, "mark entries' detail and startTime are customizable.");
diff --git a/test/fixtures/wpt/user-timing/mark-measure-feature-detection.html b/test/fixtures/wpt/user-timing/mark-measure-feature-detection.html
new file mode 100644
index 00000000000000..6f1ad489e95680
--- /dev/null
+++ b/test/fixtures/wpt/user-timing/mark-measure-feature-detection.html
@@ -0,0 +1,36 @@
+<!DOCTYPE HTML>
+<meta charset=utf-8>
+<title>User Timing: L2 vs L3 feature detection</title>
+<script src="/resources/testharness.js"></script>
+<script src="/resources/testharnessreport.js"></script>
+<script>
+  test(() => {
+    // Feature detection for PerformanceMark.
+    assert_equals(typeof(PerformanceMark.prototype), "object");
+    // Test for UserTiming L3.
+    if (PerformanceMark.prototype.hasOwnProperty('detail')) {
+      assert_equals(typeof(performance.mark("mark")), "object",
+        "performance.mark should return an object in UserTiming L3.");
+    }
+    // Test for UserTiming L2.
+    else {
+      assert_equals(typeof(performance.mark("mark")), "undefined",
+        "performance.mark should be void in UserTiming L2.");
+    }
+  }, "Test PerformanceMark existence and feature detection");
+
+  test(() => {
+    // Feature detection for PerformanceMeasure.
+    assert_equals(typeof(PerformanceMeasure.prototype), "object");
+    // Test for UserTiming L3.
+    if (PerformanceMeasure.prototype.hasOwnProperty('detail')) {
+      assert_equals(typeof(performance.measure("measure")), "object",
+        "performance.measure should return an object in UserTiming L3.");
+    }
+    // Test for UserTiming L2.
+    else {
+      assert_equals(typeof(performance.measure("measure")), "undefined",
+        "performance.measure should be void in UserTiming L2.");
+    }
+  }, "Test PerformanceMeasure existence and feature detection");
+</script>
diff --git a/test/fixtures/wpt/user-timing/mark-measure-return-objects.any.js b/test/fixtures/wpt/user-timing/mark-measure-return-objects.any.js
new file mode 100644
index 00000000000000..bb15c5839818ba
--- /dev/null
+++ b/test/fixtures/wpt/user-timing/mark-measure-return-objects.any.js
@@ -0,0 +1,37 @@
+async_test(function (t) {
+  self.performance.clearMeasures();
+  const measure = self.performance.measure("measure1");
+  assert_true(measure instanceof PerformanceMeasure);
+  t.done();
+}, "L3: performance.measure(name) should return an entry.");
+
+async_test(function (t) {
+  self.performance.clearMeasures();
+  const measure = self.performance.measure("measure2",
+      { start: 12, end: 23 });
+  assert_true(measure instanceof PerformanceMeasure);
+  t.done();
+}, "L3: performance.measure(name, param1) should return an entry.");
+
+async_test(function (t) {
+  self.performance.clearMeasures();
+  self.performance.mark("1");
+  self.performance.mark("2");
+  const measure = self.performance.measure("measure3", "1", "2");
+  assert_true(measure instanceof PerformanceMeasure);
+  t.done();
+}, "L3: performance.measure(name, param1, param2) should return an entry.");
+
+async_test(function (t) {
+  self.performance.clearMarks();
+  const mark = self.performance.mark("mark1");
+  assert_true(mark instanceof PerformanceMark);
+  t.done();
+}, "L3: performance.mark(name) should return an entry.");
+
+async_test(function (t) {
+  self.performance.clearMarks();
+  const mark = self.performance.mark("mark2", { startTime: 34 });
+  assert_true(mark instanceof PerformanceMark);
+  t.done();
+}, "L3: performance.mark(name, param) should return an entry.");
diff --git a/test/fixtures/wpt/user-timing/mark.any.js b/test/fixtures/wpt/user-timing/mark.any.js
new file mode 100644
index 00000000000000..7e814d2074ca8b
--- /dev/null
+++ b/test/fixtures/wpt/user-timing/mark.any.js
@@ -0,0 +1,118 @@
+// test data
+var testThreshold = 20;
+
+var expectedTimes = new Array();
+
+function match_entries(entries, index)
+{
+    var entry = entries[index];
+    var match = self.performance.getEntriesByName("mark")[index];
+    assert_equals(entry.name, match.name, "entry.name");
+    assert_equals(entry.startTime, match.startTime, "entry.startTime");
+    assert_equals(entry.entryType, match.entryType, "entry.entryType");
+    assert_equals(entry.duration, match.duration, "entry.duration");
+}
+
+function filter_entries_by_type(entryList, entryType)
+{
+    var testEntries = new Array();
+
+    // filter entryList
+    for (var i in entryList)
+    {
+        if (entryList[i].entryType == entryType)
+        {
+            testEntries.push(entryList[i]);
+        }
+    }
+
+    return testEntries;
+}
+
+test(function () {
+  // create first mark
+  self.performance.mark("mark");
+
+  expectedTimes[0] = self.performance.now();
+
+  const entries = self.performance.getEntriesByName("mark");
+  assert_equals(entries.length, 1);
+}, "Entry 0 is properly created");
+
+test(function () {
+    // create second, duplicate mark
+    self.performance.mark("mark");
+
+    expectedTimes[1] = self.performance.now();
+
+    const entries = self.performance.getEntriesByName("mark");
+    assert_equals(entries.length, 2);
+
+}, "Entry 1 is properly created");
+
+function test_mark(index) {
+   test(function () {
+       const entries = self.performance.getEntriesByName("mark");
+       assert_equals(entries[index].name, "mark", "Entry has the proper name");
+   }, "Entry " + index + " has the proper name");
+
+   test(function () {
+       const entries = self.performance.getEntriesByName("mark");
+       assert_approx_equals(entries[index].startTime, expectedTimes[index], testThreshold);
+   }, "Entry " + index + " startTime is approximately correct (up to " + testThreshold +
+              "ms difference allowed)");
+
+   test(function () {
+       const entries = self.performance.getEntriesByName("mark");
+       assert_equals(entries[index].entryType, "mark");
+   }, "Entry " + index + " has the proper entryType");
+
+   test(function () {
+       const entries = self.performance.getEntriesByName("mark");
+       assert_equals(entries[index].duration, 0);
+   }, "Entry " + index +  " duration == 0");
+
+   test(function () {
+    const entries = self.performance.getEntriesByName("mark", "mark");
+    assert_equals(entries[index].name, "mark");
+   }, "getEntriesByName(\"mark\", \"mark\")[" + index + "] returns an " +
+                "object containing a \"mark\" mark");
+
+   test(function () {
+    const entries = self.performance.getEntriesByName("mark", "mark");
+    match_entries(entries, index);
+   }, "The mark returned by getEntriesByName(\"mark\", \"mark\")[" + index
+      + "] matches the mark returned by " +
+              "getEntriesByName(\"mark\")[" + index + "]");
+
+   test(function () {
+    const entries = filter_entries_by_type(self.performance.getEntries(), "mark");
+    assert_equals(entries[index].name, "mark");
+   }, "getEntries()[" + index + "] returns an " +
+                "object containing a \"mark\" mark");
+
+   test(function () {
+    const entries = filter_entries_by_type(self.performance.getEntries(), "mark");
+    match_entries(entries, index);
+   }, "The mark returned by getEntries()[" + index
+      + "] matches the mark returned by " +
+              "getEntriesByName(\"mark\")[" + index + "]");
+
+   test(function () {
+    const entries = self.performance.getEntriesByType("mark");
+    assert_equals(entries[index].name, "mark");
+   }, "getEntriesByType(\"mark\")[" + index + "] returns an " +
+                "object containing a \"mark\" mark");
+
+   test(function () {
+    const entries = self.performance.getEntriesByType("mark");
+    match_entries(entries, index);
+   }, "The mark returned by getEntriesByType(\"mark\")[" + index
+      + "] matches the mark returned by " +
+              "getEntriesByName(\"mark\")[" + index + "]");
+
+}
+
+for (var i = 0; i < expectedTimes.length; i++) {
+  test_mark(i);
+}
diff --git a/test/fixtures/wpt/user-timing/mark.html b/test/fixtures/wpt/user-timing/mark.html
new file mode 100644
index 00000000000000..e03e9e6247adab
--- /dev/null
+++ b/test/fixtures/wpt/user-timing/mark.html
@@ -0,0 +1,58 @@
+<!DOCTYPE html>
+<html>
+<head>
+<meta charset="utf-8" />
+<title>functionality test of window.performance.mark</title>
+<link rel="author" title="Intel" href="http://www.intel.com/" />
+<link rel="help" href="http://www.w3.org/TR/user-timing/#extensions-performance-interface"/>
+<script src="/resources/testharness.js"></script>
+<script src="/resources/testharnessreport.js"></script>
+<script src="/common/performance-timeline-utils.js"></script>
+<script src="resources/webperftestharness.js"></script>
+<script src="resources/webperftestharnessextension.js"></script>
+<script>
+setup({ explicit_done: true });
+
+function onload_test()
+{
+    const entrylist_checker = new performance_entrylist_checker('mark');
+    const string_mark_names = mark_names.map(function (x) { return String(x)});
+
+    test_equals(performance.getEntriesByType("mark").length, 0, 'There should be ' + 0 + ' marks');
+    mark_names.forEach(function(name) {
+        performance.mark(name);
+    });
+    let mark_entrylist = performance.getEntriesByType('mark');
+
+    entrylist_checker.entrylist_check(mark_entrylist, mark_names.length, string_mark_names, 'Checking all entries.');
+
+    for (let i = 0; i < mark_entrylist.length; ++i)
+    {
+        const mark_entrylist_by_name = performance.getEntriesByName(mark_entrylist[i].name, 'mark');
+        entrylist_checker.entrylist_check(mark_entrylist_by_name, 1, string_mark_names,
+            'First loop: checking entry of name "' + mark_entrylist[i].name + '".');
+    }
+
+    mark_names.forEach(function(name) {
+        performance.mark(name);
+    });
+    mark_entrylist = performance.getEntriesByType('mark');
+    entrylist_checker.entrylist_check(mark_entrylist, mark_names.length * 2, string_mark_names, 'Checking all doubly marked entries.');
+
+    for (let i = 0; i < mark_entrylist.length; ++i)
+    {
+        const mark_entrylist_by_name = performance.getEntriesByName(mark_entrylist[i].name, 'mark');
+        entrylist_checker.entrylist_check(mark_entrylist_by_name, 2, string_mark_names,
+            'Second loop step ' + i + ': checking entries of name "' + mark_entrylist[i].name + '".');
+    }
+
+    done();
+}
+</script>
+</head>
+<body onload=onload_test()>
+    <h1>Description</h1>
+    <p>This test validates functionality of the interface window.performance.mark.</p>
+    <div id="log"></div>
+</body>
+</html>
diff --git a/test/fixtures/wpt/user-timing/mark_exceptions.html b/test/fixtures/wpt/user-timing/mark_exceptions.html
new file mode 100644
index 00000000000000..b445c6b8778ae7
--- /dev/null
+++ b/test/fixtures/wpt/user-timing/mark_exceptions.html
@@ -0,0 +1,41 @@
+<!DOCTYPE html>
+<html>
+    <head>
+        <meta charset="UTF-8" />
+        <title>window.performance User Timing mark() method is throwing the proper exceptions</title>
+        <link rel="author" title="Microsoft" href="http://www.microsoft.com/" />
+        <link rel="help" href="http://w3c.github.io/user-timing/#dom-performance-mark"/>
+        <script src="/resources/testharness.js"></script>
+        <script src="/resources/testharnessreport.js"></script>
+        <script src="resources/webperftestharness.js"></script>
+
+    <script>
+function test_exception(attrName) {
+    test(function () {
+        assert_throws_dom("SyntaxError", function () {
+            window.performance.mark(attrName);
+        })
+    }, "window.performance.mark(\"" + attrName + "\") throws a SyntaxError exception.");
+}
+
+test(() => {
+    assert_throws_js(TypeError, function() {
+        window.performance.mark();
+    });
+}, 'window.performance.mark() throws a TypeError exception.')
+
+// loop through mark scenarios
+for (var i in timingAttributes) {
+    test_exception(timingAttributes[i]);
+}
+    </script>
+    </head>
+    <body>
+        <h1>Description</h1>
+        <p>This test validates that the performance.mark() method throws a SYNTAX_ERR exception whenever a navigation
+           timing attribute is provided for the name parameter.
+        </p>
+
+        <div id="log"></div>
+    </body>
+</html>
diff --git a/test/fixtures/wpt/user-timing/measure-exceptions.html b/test/fixtures/wpt/user-timing/measure-exceptions.html
new file mode 100644
index 00000000000000..2836eaee2a86c1
--- /dev/null
+++ b/test/fixtures/wpt/user-timing/measure-exceptions.html
@@ -0,0 +1,49 @@
+<!DOCTYPE html>
+<html>
+<head>
+    This tests that 'performance.measure' throws exceptions with reasonable messages.
+</head>
+<body>
+<script src="/resources/testharness.js"></script>
+<script src="/resources/testharnessreport.js"></script>
+<script>
+    window.performance.clearMarks();
+    window.performance.clearMeasures();
+
+    window.performance.mark('mark');
+
+    const eventMarks = [
+        'unloadEventStart',
+        'unloadEventEnd',
+        'redirectStart',
+        'redirectEnd',
+        'secureConnectionStart',
+        'domInteractive',
+        'domContentLoadedEventStart',
+        'domContentLoadedEventEnd',
+        'domComplete',
+        'loadEventStart',
+        'loadEventEnd',
+    ];
+    eventMarks.forEach(function(name) {
+        test(()=>{
+            assert_throws_dom("InvalidAccessError", ()=>{
+                window.performance.measure("measuring", name, "mark");
+            }, "Should throw");
+        }, `Passing '${name}' as a mark to measure API should cause error when the mark is empty.`);
+    });
+
+    const args = [
+        51.15,  // Verify that number is parsed as string, not number.
+        "DoesNotExist", // Non-existant mark name should cause error.
+    ];
+    args.forEach(each => {
+        test(()=>{
+            assert_throws_dom("SyntaxError", ()=>{
+                window.performance.measure("measuring", each, "mark");
+            }, "Should throw");
+        }, `Passing ${each} as a mark to measure API should cause error.`);
+    });
+</script>
+</body>
+</html>
\ No newline at end of file
diff --git a/test/fixtures/wpt/user-timing/measure-l3.any.js b/test/fixtures/wpt/user-timing/measure-l3.any.js
new file mode 100644
index 00000000000000..24c27c483515ed
--- /dev/null
+++ b/test/fixtures/wpt/user-timing/measure-l3.any.js
@@ -0,0 +1,35 @@
+// META: script=resources/user-timing-helper.js
+
+function endTime(entry) {
+  return entry.startTime + entry.duration;
+}
+
+test(function() {
+  performance.clearMarks();
+  performance.clearMeasures();
+  const markEntry = performance.mark("mark", {startTime: 123});
+  const measureEntry = performance.measure("A", undefined, "mark");
+  assert_equals(measureEntry.startTime, 0);
+  assert_equals(endTime(measureEntry), markEntry.startTime);
+}, "When the end mark is given and the start is unprovided, the end time of the measure entry should be the end mark's time, the start time should be 0.");
+
+test(function() {
+  performance.clearMarks();
+  performance.clearMeasures();
+  const markEntry = performance.mark("mark", {startTime: 123});
+  const endMin = performance.now();
+  const measureEntry = performance.measure("A", "mark", undefined);
+  const endMax = performance.now();
+  assert_equals(measureEntry.startTime, markEntry.startTime);
+  assert_greater_than_equal(endTime(measureEntry), endMin);
+  assert_greater_than_equal(endMax, endTime(measureEntry));
+}, "When the start mark is given and the end is unprovided, the start time of the measure entry should be the start mark's time, the end should be now.");
+
+test(function() {
+  performance.clearMarks();
+  performance.clearMeasures();
+  const markEntry = performance.mark("mark", {startTime: 123});
+  const measureEntry = performance.measure("A", "mark", "mark");
+  assert_equals(endTime(measureEntry), markEntry.startTime);
+  assert_equals(measureEntry.startTime, markEntry.startTime);
+}, "When start and end mark are both given, the start time and end time of the measure entry should be the the marks' time, repectively");
diff --git a/test/fixtures/wpt/user-timing/measure-with-dict.any.js b/test/fixtures/wpt/user-timing/measure-with-dict.any.js
new file mode 100644
index 00000000000000..b452feb0de6fbb
--- /dev/null
+++ b/test/fixtures/wpt/user-timing/measure-with-dict.any.js
@@ -0,0 +1,112 @@
+// META: script=resources/user-timing-helper.js
+
+function cleanupPerformanceTimeline() {
+    performance.clearMarks();
+    performance.clearMeasures();
+}
+
+async_test(function (t) {
+    this.add_cleanup(cleanupPerformanceTimeline);
+    let measureEntries = [];
+    const timeStamp1 = 784.4;
+    const timeStamp2 = 1234.5;
+    const timeStamp3 = 66.6;
+    const timeStamp4 = 5566;
+    const expectedEntries =
+        [{ entryType: "measure", name: "measure1", detail: null, startTime: 0 },
+        { entryType: "measure", name: "measure2", detail: null, startTime: 0 },
+        { entryType: "measure", name: "measure3", detail: null, startTime: 0 },
+        { entryType: "measure", name: "measure4", detail: null },
+        { entryType: "measure", name: "measure5", detail: null, startTime: 0 },
+        { entryType: "measure", name: "measure6", detail: null, startTime: timeStamp1 },
+        { entryType: "measure", name: "measure7", detail: null, startTime: timeStamp1, duration: timeStamp2 - timeStamp1 },
+        { entryType: "measure", name: "measure8", detail: null, startTime: 0 },
+        { entryType: "measure", name: "measure9", detail: null, startTime: 0 },
+        { entryType: "measure", name: "measure10", detail: null, startTime: timeStamp1 },
+        { entryType: "measure", name: "measure11", detail: null, startTime: timeStamp3 },
+        { entryType: "measure", name: "measure12", detail: null, startTime: 0 },
+        { entryType: "measure", name: "measure13", detail: null, startTime: 0 },
+        { entryType: "measure", name: "measure14", detail: null, startTime: timeStamp3, duration: timeStamp1 - timeStamp3 },
+        { entryType: "measure", name: "measure15", detail: null, startTime: timeStamp1, duration: timeStamp2 - timeStamp1 },
+        { entryType: "measure", name: "measure16", detail: null, startTime: timeStamp1 },
+        { entryType: "measure", name: "measure17", detail: { customInfo: 159 }, startTime: timeStamp3, duration: timeStamp2 - timeStamp3 },
+        { entryType: "measure", name: "measure18", detail: null, startTime: timeStamp1, duration: timeStamp2 - timeStamp1 },
+        { entryType: "measure", name: "measure19", detail: null, startTime: timeStamp1, duration: timeStamp2 - timeStamp1 },
+        { entryType: "measure", name: "measure20", detail: null, startTime: 0 },
+        { entryType: "measure", name: "measure21", detail: null, startTime: 0 },
+        { entryType: "measure", name: "measure22", detail: null, startTime: 0 },
+        { entryType: "measure", name: "measure23", detail: null, startTime: 0 }];
+    const observer = new PerformanceObserver(
+        t.step_func(function (entryList, obs) {
+          measureEntries =
+            measureEntries.concat(entryList.getEntries());
+          if (measureEntries.length >= expectedEntries.length) {
+            checkEntries(measureEntries, expectedEntries);
+            observer.disconnect();
+            t.done();
+          }
+        })
+      );
+    observer.observe({ entryTypes: ["measure"] });
+    self.performance.mark("mark1", { detail: { randomInfo: 3 }, startTime: timeStamp1 });
+    self.performance.mark("mark2", { startTime: timeStamp2 });
+
+    const returnedEntries = [];
+    returnedEntries.push(self.performance.measure("measure1"));
+    returnedEntries.push(self.performance.measure("measure2", undefined));
+    returnedEntries.push(self.performance.measure("measure3", null));
+    returnedEntries.push(self.performance.measure("measure4", 'mark1'));
+    returnedEntries.push(
+        self.performance.measure("measure5", null, 'mark1'));
+    returnedEntries.push(
+        self.performance.measure("measure6", 'mark1', undefined));
+    returnedEntries.push(
+        self.performance.measure("measure7", 'mark1', 'mark2'));
+    returnedEntries.push(
+        self.performance.measure("measure8", {}));
+    returnedEntries.push(
+        self.performance.measure("measure9", { start: undefined }));
+    returnedEntries.push(
+        self.performance.measure("measure10", { start: 'mark1' }));
+    returnedEntries.push(
+        self.performance.measure("measure11", { start: timeStamp3 }));
+    returnedEntries.push(
+        self.performance.measure("measure12", { end: undefined }));
+    returnedEntries.push(
+        self.performance.measure("measure13", { end: 'mark1' }));
+    returnedEntries.push(
+        self.performance.measure("measure14", { start: timeStamp3, end: 'mark1' }));
+    returnedEntries.push(
+        self.performance.measure("measure15", { start: timeStamp1, end: timeStamp2, detail: undefined }));
+    returnedEntries.push(
+        self.performance.measure("measure16", { start: 'mark1', end: undefined, detail: null }));
+    returnedEntries.push(
+        self.performance.measure("measure17", { start: timeStamp3, end: 'mark2', detail: { customInfo: 159 }}));
+    returnedEntries.push(
+        self.performance.measure("measure18", { start: timeStamp1, duration: timeStamp2 - timeStamp1 }));
+    returnedEntries.push(
+        self.performance.measure("measure19", { duration: timeStamp2 - timeStamp1, end: timeStamp2 }));
+    // {}, null, undefined, invalid-dict passed to startOrOptions are interpreted as start time being 0.
+    returnedEntries.push(self.performance.measure("measure20", {}, 'mark1'));
+    returnedEntries.push(self.performance.measure("measure21", null, 'mark1'));
+    returnedEntries.push(self.performance.measure("measure22", undefined, 'mark1'));
+    returnedEntries.push(self.performance.measure("measure23", { invalidDict:1 }, 'mark1'));
+    checkEntries(returnedEntries, expectedEntries);
+}, "measure entries' detail and start/end are customizable");
+
+test(function() {
+    this.add_cleanup(cleanupPerformanceTimeline);
+    assert_throws_js(TypeError, function() {
+      self.performance.measure("optionsAndNumberEnd", {'start': 2}, 12);
+    }, "measure should throw a TypeError when passed an options object and an end time");
+    assert_throws_js(TypeError, function() {
+      self.performance.measure("optionsAndMarkEnd", {'start': 2}, 'mark1');
+    }, "measure should throw a TypeError when passed an options object and an end mark");
+    assert_throws_js(TypeError, function() {
+      self.performance.measure("negativeStartInOptions", {'start': -1});
+    }, "measure cannot have a negative time stamp.");
+    assert_throws_js(TypeError, function() {
+      self.performance.measure("negativeEndInOptions", {'end': -1});
+    }, "measure cannot have a negative time stamp for end.");
+}, "measure should throw a TypeError when passed an invalid argument combination");
+
diff --git a/test/fixtures/wpt/user-timing/measure.html b/test/fixtures/wpt/user-timing/measure.html
new file mode 100644
index 00000000000000..40f71a3362b581
--- /dev/null
+++ b/test/fixtures/wpt/user-timing/measure.html
@@ -0,0 +1,362 @@
+
+<!DOCTYPE html>
+<html>
+    <head>
+        <meta charset="UTF-8" />
+        <title>window.performance User Timing measure() method is working properly</title>
+        <link rel="author" title="Microsoft" href="http://www.microsoft.com/" />
+        <link rel="help" href="https://w3c.github.io/user-timing/#dom-performance-measure"/>
+        <script src="/resources/testharness.js"></script>
+        <script src="/resources/testharnessreport.js"></script>
+        <script src="/common/performance-timeline-utils.js"></script>
+        <script src="resources/webperftestharness.js"></script>
+
+    <script>
+        // test data
+        var startMarkName = "mark_start";
+        var startMarkValue;
+        var endMarkName = "mark_end";
+        var endMarkValue;
+        var measures;
+        var testThreshold = 20;
+
+        // test measures
+        var measureTestDelay = 200;
+        var TEST_MEASURES =
+        [
+            {
+                name:                   "measure_no_start_no_end",
+                startMark:              undefined,
+                endMark:                undefined,
+                startTime:              undefined,
+                duration:               undefined,
+                entryType:              "measure",
+                entryMatch:             undefined,
+                order:                  undefined,
+                found:                  false
+            },
+            {
+                name:                   "measure_start_no_end",
+                startMark:              "mark_start",
+                endMark:                undefined,
+                startTime:              undefined,
+                duration:               undefined,
+                entryType:              "measure",
+                entryMatch:             undefined,
+                order:                  undefined,
+                found:                  false
+            },
+            {
+                name:                   "measure_start_end",
+                startMark:              "mark_start",
+                endMark:                "mark_end",
+                startTime:              undefined,
+                duration:               undefined,
+                entryType:              "measure",
+                entryMatch:             undefined,
+                order:                  undefined,
+                found:                  false
+            },
+            {
+                name:                   "measure_no_start_end",
+                startMark:              undefined,
+                endMark:                "mark_end",
+                startTime:              undefined,
+                duration:               undefined,
+                entryType:              "measure",
+                entryMatch:             undefined,
+                order:                  undefined,
+                found:                  false
+            },
+            // intentional duplicate of the first measure, used to confirm names can be re-used
+            {
+                name:                   "measure_no_start_no_end",
+                startMark:              undefined,
+                endMark:                undefined,
+                startTime:              undefined,
+                duration:               undefined,
+                entryType:              "measure",
+                entryMatch:             undefined,
+                order:                  undefined,
+                found:                  false
+            }
+        ];
+        // the index of the duplicate "measure_no_start_no_end"
+        const duplicate_index = TEST_MEASURES.map(m=>m.name).lastIndexOf('measure_no_start_no_end');
+
+        setup({explicit_done: true});
+
+        test_namespace();
+
+        function onload_test()
+        {
+            // test for existence of User Timing and Performance Timeline interface
+            if (!has_required_interfaces())
+            {
+                test_true(false,
+                          "The User Timing and Performance Timeline interfaces, which are required for this test, " +
+                          "are defined.");
+
+                done();
+            }
+            else
+            {
+                // create the start mark for the test measures
+                window.performance.mark(startMarkName);
+
+                // get the start mark's value
+                startMarkValue = window.performance.getEntriesByName(startMarkName)[0].startTime;
+
+                // create the test end mark using the test delay; this will allow for a significant difference between
+                // the mark values that should be represented in the duration of measures using these marks
+                step_timeout(measure_test_cb, measureTestDelay);
+            }
+        }
+
+        function measure_test_cb()
+        {
+            // create the end mark for the test measures
+            window.performance.mark(endMarkName);
+
+            // get the end mark's value
+            endMarkValue = window.performance.getEntriesByName(endMarkName)[0].startTime;
+
+            // loop through all measure scenarios and create the corresponding measures
+            for (var i in TEST_MEASURES)
+            {
+                var scenario = TEST_MEASURES[i];
+
+                if (scenario.startMark == undefined && scenario.endMark == undefined)
+                {
+                    // both startMark and endMark are undefined, don't provide either parameters
+                    window.performance.measure(scenario.name);
+
+                    // when startMark isn't provided to the measure() call, a DOMHighResTimeStamp corresponding
+                    // to the navigationStart attribute with a timebase of the same attribute is used; this is
+                    // equivalent to 0
+                    scenario.startTime = 0;
+
+                    // when endMark isn't provided to the measure() call, a DOMHighResTimeStamp corresponding to
+                    // the current time with a timebase of the navigationStart attribute is used
+                    scenario.duration = (new Date()) - window.performance.timing.navigationStart;
+                }
+                else if (scenario.startMark != undefined && scenario.endMark == undefined)
+                {
+                    // only startMark is defined, provide startMark and don't provide endMark
+                    window.performance.measure(scenario.name, scenario.startMark);
+
+                    // when startMark is provided to the measure() call, the value of the mark whose name is
+                    // provided is used for the startMark
+                    scenario.startTime = startMarkValue;
+
+                    // when endMark isn't provided to the measure() call, a DOMHighResTimeStamp corresponding to
+                    // the current time with a timebase of the navigationStart attribute is used
+                    scenario.duration = window.performance.now() -
+                                                startMarkValue;
+                }
+                else if (scenario.startMark != undefined && scenario.endMark != undefined)
+                {
+                    // both startMark and endMark are defined, provide both parameters
+                    window.performance.measure(scenario.name, scenario.startMark, scenario.endMark);
+
+                    // when startMark is provided to the measure() call, the value of the mark whose name is
+                    // provided is used for the startMark
+                    scenario.startTime = startMarkValue;
+
+                    // when endMark is provided to the measure() call, the value of the mark whose name is
+                    // provided is used for the endMark
+                    scenario.duration = endMarkValue - startMarkValue;
+                }
+                else if (scenario.startMark == undefined && scenario.endMark != undefined)
+                {
+                    // endMark is defined but startMark is undefined, provide both parameters
+                    window.performance.measure(scenario.name, scenario.startMark, scenario.endMark);
+
+                    // when startMark isn't provided to the measure() call, a DOMHighResTimeStamp corresponding
+                    // to the navigationStart attribute with a timebase of the same attribute is used; this is
+                    // equivalent to 0
+                    scenario.startTime = 0;
+
+                    // when endMark is provided to the measure() call, the value of the mark whose name is
+                    // provided is used for the endMark
+                    scenario.duration = endMarkValue;
+                } else
+                {
+                    test_true(false, 'Test measure scenario unhandled');
+                }
+            }
+
+            // test that expected measures are returned by getEntriesByName
+            for (var i in TEST_MEASURES)
+            {
+                entries = window.performance.getEntriesByName(TEST_MEASURES[i].name);
+                // for all test measures, the test will be validate the test measure against the first entry returned
+                // by getEntriesByName(), except for the last measure, where since it is a duplicate measure, the test
+                // will validate it against the second entry returned by getEntriesByName()
+                test_measure(entries[(i == duplicate_index ? 1 : 0)],
+                            "window.performance.getEntriesByName(\"" + TEST_MEASURES[i].name + "\")[" +
+                            (i == duplicate_index ? 1 : 0) + "]",
+                            TEST_MEASURES[i].name,
+                            TEST_MEASURES[i].startTime,
+                            TEST_MEASURES[i].duration);
+                TEST_MEASURES[i].entryMatch = entries[(i == duplicate_index ? 1 : 0)];
+            }
+
+            // test that expected measures are returned by getEntriesByName with the entryType parameter provided
+            for (var i in TEST_MEASURES)
+            {
+                entries = window.performance.getEntriesByName(TEST_MEASURES[i].name, "measure");
+
+                test_true(match_entries(entries[(i == duplicate_index ? 1 : 0)], TEST_MEASURES[i].entryMatch),
+                          "window.performance.getEntriesByName(\"" + TEST_MEASURES[i].name + "\", \"measure\")[" +
+                          (i == duplicate_index ? 1 : 0) + "] returns an object containing the \"" + TEST_MEASURES[i].name +
+                          "\" measure in the correct order, and its value matches the \"" + TEST_MEASURES[i].name +
+                          "\" measure returned by window.performance.getEntriesByName(\"" + TEST_MEASURES[i].name +
+                          "\")");
+            }
+
+            // test that expected measures are returned by getEntries
+            entries = get_test_entries(window.performance.getEntries(), "measure");
+
+            test_measure_list(entries, "window.performance.getEntries()", TEST_MEASURES);
+
+            // test that expected measures are returned by getEntriesByType
+            entries = window.performance.getEntriesByType("measure");
+
+            test_measure_list(entries, "window.performance.getEntriesByType(\"measure\")", TEST_MEASURES);
+
+            done();
+        }
+
+        function match_entries(entry1, entry2, threshold)
+        {
+            if (threshold == undefined)
+            {
+                threshold = 0;
+            }
+
+            var pass = true;
+
+            // match name
+            pass = pass && (entry1.name == entry2.name);
+
+            // match startTime
+            pass = pass && (Math.abs(entry1.startTime - entry2.startTime) <= testThreshold);
+
+            // match entryType
+            pass = pass && (entry1.entryType == entry2.entryType);
+
+            // match duration
+            pass = pass && (Math.abs(entry1.duration - entry2.duration) <= testThreshold);
+
+            return pass;
+        }
+
+        function test_measure(measureEntry, measureEntryCommand, expectedName, expectedStartTime, expectedDuration)
+        {
+            // test name
+            test_true(measureEntry.name == expectedName, measureEntryCommand + ".name == \"" + expectedName + "\"");
+
+            // test startTime; since for a mark, the startTime is always equal to a mark's value or the value of a
+            // navigation timing attribute, the actual startTime should match the expected value exactly
+            test_true(Math.abs(measureEntry.startTime - expectedStartTime) == 0,
+                      measureEntryCommand + ".startTime is correct");
+
+            // test entryType
+            test_true(measureEntry.entryType == "measure", measureEntryCommand + ".entryType == \"measure\"");
+
+            // test duration, allow for an acceptable threshold in the difference between the actual duration and the
+            // expected value for the duration
+            test_true(Math.abs(measureEntry.duration - expectedDuration) <= testThreshold, measureEntryCommand +
+                      ".duration is approximately correct (up to " + testThreshold + "ms difference allowed)");
+        }
+
+        function test_measure_list(measureEntryList, measureEntryListCommand, measureScenarios)
+        {
+            // give all entries a "found" property that can be set to ensure it isn't tested twice
+            for (var i in measureEntryList)
+            {
+                measureEntryList[i].found = false;
+            }
+
+            for (var i in measureScenarios)
+            {
+                measureScenarios[i].found = false;
+
+                for (var j in measureEntryList)
+                {
+                    if (match_entries(measureEntryList[j], measureScenarios[i]) && !measureEntryList[j].found)
+                    {
+                        test_true(match_entries(measureEntryList[j], measureScenarios[i].entryMatch),
+                                  measureEntryListCommand + " returns an object containing the \"" +
+                                  measureScenarios[i].name + "\" measure, and it's value matches the measure " +
+                                  "returned by window.performance.getEntriesByName(\"" + measureScenarios[i].name +
+                                  "\")[" + (i == duplicate_index ? 1 : 0) + "].");
+
+                        measureEntryList[j].found = true;
+                        measureScenarios[i].found = true;
+                        break;
+                    }
+                }
+
+                if (!measureScenarios[i].found)
+                {
+                    test_true(false,
+                              measureEntryListCommand + " returns an object containing the \"" +
+                              measureScenarios[i].name + "\" measure.");
+                }
+            }
+
+            // verify order of output of getEntriesByType
+            var startTimeCurr = 0;
+            var pass = true;
+            for (var i in measureEntryList)
+            {
+                if (measureEntryList[i].startTime < startTimeCurr)
+                {
+                    pass = false;
+                }
+                startTimeCurr = measureEntryList[i].startTime;
+            }
+            test_true(pass,
+                      measureEntryListCommand + " returns an object containing all test " +
+                      "measures in order.");
+        }
+
+        function get_test_entries(entryList, entryType)
+        {
+            var testEntries = new Array();
+
+            // filter entryList
+            for (var i in entryList)
+            {
+                if (entryList[i].entryType == entryType)
+                {
+                    testEntries.push(entryList[i]);
+                }
+            }
+
+            return testEntries;
+        }
+    </script>
+    </head>
+    <body onload="onload_test();">
+        <h1>Description</h1>
+        <p>This test validates that the performance.measure() method is working properly. This test creates the
+           following measures to test this method:
+            <ul>
+                <li>"measure_no_start_no_end": created using a measure() call without a startMark or endMark
+                    provided</li>
+                <li>"measure_start_no_end": created using a measure() call with only the startMark provided</li>
+                <li>"measure_start_end": created using a measure() call with both a startMark or endMark provided</li>
+                <li>"measure_no_start_end": created using a measure() call with only the endMark provided</li>
+                <li>"measure_no_start_no_end": duplicate of the first measure, used to confirm names can be re-used</li>
+            </ul>
+           After creating each measure, the existence of these measures is validated by calling
+           performance.getEntriesByName() (both with and without the entryType parameter provided),
+           performance.getEntriesByType(), and performance.getEntries()
+        </p>
+
+        <div id="log"></div>
+    </body>
+</html>
diff --git a/test/fixtures/wpt/user-timing/measure_associated_with_navigation_timing.html b/test/fixtures/wpt/user-timing/measure_associated_with_navigation_timing.html
new file mode 100644
index 00000000000000..702e3d5f87f39e
--- /dev/null
+++ b/test/fixtures/wpt/user-timing/measure_associated_with_navigation_timing.html
@@ -0,0 +1,57 @@
+<!DOCTYPE html>
+<html>
+<head>
+<meta charset="utf-8" />
+<title>functionality test of window.performance.measure</title>
+<link rel="author" title="Intel" href="http://www.intel.com/" />
+<link rel="help" href="http://www.w3.org/TR/user-timing/#extensions-performance-interface"/>
+<script src="/resources/testharness.js"></script>
+<script src="/resources/testharnessreport.js"></script>
+<script src="/common/performance-timeline-utils.js"></script>
+<script src="resources/webperftestharness.js"></script>
+<script src="resources/webperftestharnessextension.js"></script>
+<script>
+setup({ explicit_done: true });
+
+function onload_test()
+{
+    const measures_for_timing_order = [
+        ['nav2now', 'navigationStart'],
+        ['loadTime', 'navigationStart', 'loadEventEnd'],
+        ['loadEventEnd2a', 'loadEventEnd', 'abc'],
+        ['nav2a', 'navigationStart', 'abc'],
+        ['domComplete2a', 'domComplete', 'abc'],
+        ['negativeValue', 1, 'navigationStart'],
+    ];
+    const context = new PerformanceContext(window.performance);
+
+    mark_names.forEach(function(name) {
+        context.mark(name);
+    });
+    measures_for_timing_order.forEach(context.initialMeasures, context);
+    test_greater_than(context.getEntriesByName('nav2now', 'measure')[0].duration, 0, 'Measure of navigationStart to now should be positive value.');
+    test_greater_than(context.getEntriesByName('loadTime', 'measure')[0].duration, 0, 'Measure of navigationStart to loadEventEnd should be positive value.');
+    test_greater_than(0, context.getEntriesByName('negativeValue', 'measure')[0].duration, 'Measure of current mark to navigationStart should be negative value.');
+    test_equals(context.getEntriesByName('loadTime', 'measure')[0].duration + context.getEntriesByName('loadEventEnd2a', 'measure')[0].duration, context.getEntriesByName('nav2a', 'measure')[0].duration, 'loadTime plus loadEventEnd to a mark "a" should equal to navigationStart to "a".');
+
+    // Following cases test for scenarios that measure names are tied twice.
+    mark_names.forEach(function(name) {
+        context.mark(name);
+    });
+    measures_for_timing_order.forEach(context.initialMeasures, context);
+
+    test_greater_than(context.getEntriesByName('nav2now', 'measure')[1].duration, context.getEntriesByName('nav2now', 'measure')[0].duration, 'Second measure of current mark to navigationStart should be negative value.');
+    test_equals(context.getEntriesByName('loadTime', 'measure')[0].duration, context.getEntriesByName('loadTime', 'measure')[1].duration, 'Measures of loadTime should have same duration.');
+    test_greater_than(context.getEntriesByName('domComplete2a', 'measure')[1].duration, context.getEntriesByName('domComplete2a', 'measure')[0].duration, 'Measure from domComplete event to most recent mark "a" should have longer duration.');
+    test_greater_than(context.getEntriesByName('negativeValue', 'measure')[0].duration, context.getEntriesByName('negativeValue', 'measure')[1].duration, 'Measure from most recent mark to navigationStart should have longer duration.');
+
+    done();
+}
+</script>
+</head>
+<body onload="setTimeout(onload_test,0)">
+    <h1>Description</h1>
+    <p>This test validates functionality of the interface window.performance.measure using keywords from the Navigation Timing spec.</p>
+    <div id="log"></div>
+</body>
+</html>
diff --git a/test/fixtures/wpt/user-timing/measure_exception.html b/test/fixtures/wpt/user-timing/measure_exception.html
new file mode 100644
index 00000000000000..5c1aa086c0fc88
--- /dev/null
+++ b/test/fixtures/wpt/user-timing/measure_exception.html
@@ -0,0 +1,34 @@
+<!DOCTYPE html>
+<html>
+<head>
+<meta charset="utf-8" />
+<title>exception test of window.performance.measure</title>
+<link rel="author" title="Intel" href="http://www.intel.com/" />
+<link rel="help" href="http://www.w3.org/TR/user-timing/#extensions-performance-interface"/>
+<script src="/resources/testharness.js"></script>
+<script src="/resources/testharnessreport.js"></script>
+<script src="/common/performance-timeline-utils.js"></script>
+<script src="resources/webperftestharness.js"></script>
+<script src="resources/webperftestharnessextension.js"></script>
+</head>
+
+<body>
+<h1>Description</h1>
+<p>This test validates all exception scenarios of method window.performance.measure in User Timing API</p>
+
+<div id="log"></div>
+<script>
+performance.mark('ExistMark');
+test_method_throw_exception('performance.measure()', TypeError);
+test_method_throw_exception('performance.measure("Exception1", "NonExistMark1")', 'SYNTAX_ERR');
+test_method_throw_exception('performance.measure("Exception2", "NonExistMark1", "navigationStart")', 'SYNTAX_ERR');
+test_method_throw_exception('performance.measure("Exception3", "navigationStart", "NonExistMark1")', 'SYNTAX_ERR');
+test_method_throw_exception('performance.measure("Exception4", "NonExistMark1", "ExistMark")', 'SYNTAX_ERR');
+test_method_throw_exception('performance.measure("Exception5", "ExistMark", "NonExistMark1")', 'SYNTAX_ERR');
+test_method_throw_exception('performance.measure("Exception6", "NonExistMark1", "NonExistMark2")', 'SYNTAX_ERR');
+test_method_throw_exception('performance.measure("Exception7", "redirectStart")', 'INVALID_ACCESS_ERR');
+test_method_throw_exception('performance.measure("Exception8", {"detail": "non-empty"})', TypeError);
+test_method_throw_exception('performance.measure("Exception9", {"start": 1, "duration": 2, "end": 3})', TypeError);
+</script>
+</body>
+</html>
diff --git a/test/fixtures/wpt/user-timing/measure_exceptions_navigation_timing.html b/test/fixtures/wpt/user-timing/measure_exceptions_navigation_timing.html
new file mode 100644
index 00000000000000..b1868b2cb6b3cb
--- /dev/null
+++ b/test/fixtures/wpt/user-timing/measure_exceptions_navigation_timing.html
@@ -0,0 +1,70 @@
+<!DOCTYPE html>
+<html>
+    <head>
+        <meta charset="UTF-8" />
+        <title>window.performance User Timing measure() method is throwing the proper exceptions</title>
+        <link rel="author" title="Microsoft" href="http://www.microsoft.com/" />
+        <link rel="help" href="https://w3c.github.io/user-timing/#dom-performance-measure"/>
+        <script src="/resources/testharness.js"></script>
+        <script src="/resources/testharnessreport.js"></script>
+        <script src="resources/webperftestharness.js"></script>
+
+    <script>
+// test data
+var zeroedNavTimingAtt = undefined;
+
+setup(function () {
+   // for testing the INVALID_ACCESS_ERR exception, find a navigation timing attribute with a value of zero
+   for (var i in timingAttributes) {
+     if (window.performance.timing[timingAttributes[i]] == 0) {
+        zeroedNavTimingAtt = timingAttributes[i];
+     }
+   }
+   if (zeroedNavTimingAtt == undefined) {
+       throw new Error("A navigation timing attribute with a value of 0 was not found to test for the " +
+                          "INVALID_ACCESS_ERR exception thrown by window.performance.measure().")
+   }
+});
+
+test(function () {
+   assert_throws_dom("InvalidAccessError", function () {
+       window.performance.measure("measure", zeroedNavTimingAtt);
+   });
+}, "window.performance.measure(\"measure\", \"" + zeroedNavTimingAtt + "\"), where \"" +
+                              zeroedNavTimingAtt + "\" is a navigation timing attribute with a value of 0, throws a " +
+                              "InvalidAccessError exception.");
+
+test(function () {
+   assert_throws_dom("InvalidAccessError", function () {
+       window.performance.measure("measure", zeroedNavTimingAtt, "responseEnd");
+   });
+}, "window.performance.measure(\"measure\", \"" + zeroedNavTimingAtt + "\", " +
+                              "\"responseEnd\"), where \"" + zeroedNavTimingAtt + "\" is a navigation timing " +
+                              "attribute with a value of 0, throws a InvalidAccessError exception.");
+
+test(function () {
+   assert_throws_dom("InvalidAccessError", function () {
+       window.performance.measure("measure", "navigationStart", zeroedNavTimingAtt);
+   });
+}, "window.performance.measure(\"measure\", \"navigationStart\", \"" + zeroedNavTimingAtt +
+                              "\"), where \"" + zeroedNavTimingAtt + "\" is a navigation timing attribute with a " +
+                              "value of 0, throws a InvalidAccessError exception.");
+
+test(function () {
+   assert_throws_dom("InvalidAccessError", function () {
+       window.performance.measure("measure", zeroedNavTimingAtt, zeroedNavTimingAtt);
+   });
+}, "window.performance.measure(\"measure\", \"" + zeroedNavTimingAtt + "\", \"" +
+                              zeroedNavTimingAtt + "\"), where \"" + zeroedNavTimingAtt + "\" is a navigation timing " +
+                              "attribute with a value of 0, throws a InvalidAccessError exception.");
+    </script>
+    </head>
+    <body>
+        <h1>Description</h1>
+        <p><code>window.performance.measure()</code> method throws a InvalidAccessError
+           whenever a navigation timing attribute with a value of zero is provided as the startMark or endMark.
+        </p>
+
+        <div id="log"></div>
+    </body>
+</html>
diff --git a/test/fixtures/wpt/user-timing/measure_navigation_timing.html b/test/fixtures/wpt/user-timing/measure_navigation_timing.html
new file mode 100644
index 00000000000000..d6480d27a261c9
--- /dev/null
+++ b/test/fixtures/wpt/user-timing/measure_navigation_timing.html
@@ -0,0 +1,205 @@
+
+<!DOCTYPE html>
+<html>
+    <head>
+        <meta charset="UTF-8" />
+        <title>window.performance User Timing clearMeasures() method is working properly with navigation timing
+               attributes</title>
+        <link rel="author" title="Microsoft" href="http://www.microsoft.com/" />
+        <link rel="help" href="https://w3c.github.io/user-timing/#dom-performance-measure"/>
+        <script src="/resources/testharness.js"></script>
+        <script src="/resources/testharnessreport.js"></script>
+        <script src="/common/performance-timeline-utils.js"></script>
+        <script src="resources/webperftestharness.js"></script>
+
+    <script>
+        // test data
+        var startMarkName = "mark_start";
+        var startMarkValue;
+        var endMarkName = "mark_end";
+        var endMarkValue;
+        var measures;
+        var testThreshold = 20;
+
+        // test measures
+        measureTestDelay = 200;
+        var TEST_MEASURES =
+        [
+            {
+                name:                   "measure_nav_start_no_end",
+                startMark:              "navigationStart",
+                endMark:                undefined,
+                exceptionTestMessage:   "window.performance.measure(\"measure_nav_start_no_end\", " +
+                                        "\"navigationStart\") ran without throwing any exceptions.",
+                expectedStartTime:      undefined,
+                expectedDuration:       undefined,
+                entryMatch:             undefined
+            },
+            {
+                name:                   "measure_nav_start_mark_end",
+                startMark:              "navigationStart",
+                endMark:                "mark_end",
+                exceptionTestMessage:   "window.performance.measure(\"measure_nav_start_end\", \"navigationStart\", " +
+                                        "\"mark_end\") ran without throwing any exceptions.",
+                expectedStartTime:      undefined,
+                expectedDuration:       undefined,
+                entryMatch:             undefined
+            },
+            {
+                name:                   "measure_mark_start_nav_end",
+                startMark:              "mark_start",
+                endMark:                "responseEnd",
+                exceptionTestMessage:   "window.performance.measure(\"measure_start_nav_end\", \"mark_start\", " +
+                                        "\"responseEnd\") ran without throwing any exceptions.",
+                expectedStartTime:      undefined,
+                expectedDuration:       undefined,
+                entryMatch:             undefined
+            },
+            {
+                name:                   "measure_nav_start_nav_end",
+                startMark:              "navigationStart",
+                endMark:                "responseEnd",
+                exceptionTestMessage:   "window.performance.measure(\"measure_nav_start_nav_end\", " +
+                                        "\"navigationStart\", \"responseEnd\") ran without throwing any exceptions.",
+                expectedStartTime:      undefined,
+                expectedDuration:       undefined,
+                entryMatch:             undefined
+            }
+        ];
+
+        setup({explicit_done: true});
+
+        test_namespace();
+
+        function onload_test()
+        {
+            // test for existence of User Timing and Performance Timeline interface
+            if (!has_required_interfaces())
+            {
+                test_true(false,
+                          "The User Timing and Performance Timeline interfaces, which are required for this test, " +
+                          "are defined.");
+
+                done();
+            }
+            else
+            {
+                // create the start mark for the test measures
+                window.performance.mark(startMarkName);
+
+                // get the start mark's value
+                startMarkValue = window.performance.getEntriesByName(startMarkName)[0].startTime;
+
+                // create the test end mark using the test delay; this will allow for a significant difference between
+                // the mark values that should be represented in the duration of measures using these marks
+                step_timeout(measure_test_cb, measureTestDelay);
+            }
+        }
+
+        function measure_test_cb()
+        {
+            // create the end mark for the test measures
+            window.performance.mark(endMarkName);
+
+            // get the end mark's value
+            endMarkValue = window.performance.getEntriesByName(endMarkName)[0].startTime;
+
+            // loop through measure scenarios
+            for (var i in TEST_MEASURES)
+            {
+                var scenario = TEST_MEASURES[i];
+
+                if (scenario.startMark != undefined && scenario.endMark == undefined)
+                {
+                    // only startMark is defined, provide startMark and don't provide endMark
+                    window.performance.measure(scenario.name, scenario.startMark);
+
+                    // when startMark is provided to the measure() call, the value of the mark or navigation
+                    // timing attribute whose name is provided is used for the startMark
+                    scenario.expectedStartTime = (timingAttributes.indexOf(scenario.startMark) != -1 ?
+                                                  window.performance.timing[scenario.startMark] -
+                                                  window.performance.timing.navigationStart :
+                                                  startMarkValue);
+
+                    // when endMark isn't provided to the measure() call, a DOMHighResTimeStamp corresponding to
+                    // the current time with a timebase of the navigationStart attribute is used
+                    scenario.expectedDuration = ((new Date()) - window.performance.timing.navigationStart) -
+                                                scenario.expectedStartTime;
+                }
+                else if (scenario.startMark != undefined && scenario.endMark != undefined)
+                {
+                    // both startMark and endMark are defined, provide both parameters
+                    window.performance.measure(scenario.name, scenario.startMark, scenario.endMark);
+
+                    // when startMark is provided to the measure() call, the value of the mark or navigation
+                    // timing attribute whose name is provided is used for the startMark
+                    scenario.expectedStartTime = (timingAttributes.indexOf(scenario.startMark) != -1 ?
+                                                  window.performance.timing[scenario.startMark] -
+                                                  window.performance.timing.navigationStart :
+                                                  startMarkValue);
+
+                    // when endMark is provided to the measure() call, the value of the mark whose name is
+                    // provided is used for the startMark
+                    scenario.expectedDuration = (timingAttributes.indexOf(scenario.endMark) != -1 ?
+                                                 window.performance.timing[scenario.endMark] -
+                                                 window.performance.timing.navigationStart :
+                                                 endMarkValue) - scenario.expectedStartTime;
+                }
+            }
+
+            // test the test measures are returned by getEntriesByName
+            for (var i in TEST_MEASURES)
+            {
+                entries = window.performance.getEntriesByName(TEST_MEASURES[i].name);
+                test_measure(entries[0],
+                            "window.performance.getEntriesByName(\"" + TEST_MEASURES[i].name + "\")[0]",
+                            TEST_MEASURES[i].name,
+                            TEST_MEASURES[i].expectedStartTime,
+                            TEST_MEASURES[i].expectedDuration);
+                TEST_MEASURES[i].entryMatch = entries[0];
+            }
+
+            done();
+        }
+
+        function test_measure(measureEntry, measureEntryCommand, expectedName, expectedStartTime, expectedDuration)
+        {
+            // test name
+            test_true(measureEntry.name == expectedName, measureEntryCommand + ".name == \"" + expectedName + "\"");
+
+            // test startTime; since for a mark, the startTime is always equal to a mark's value or the value of a
+            // navigation timing attribute, the actual startTime should match the expected value exactly
+            test_true(Math.abs(measureEntry.startTime - expectedStartTime) == 0,
+                      measureEntryCommand + ".startTime is correct");
+
+            // test entryType
+            test_true(measureEntry.entryType == "measure", measureEntryCommand + ".entryType == \"measure\"");
+
+            // test duration, allow for an acceptable threshold in the difference between the actual duration and the
+            // expected value for the duration
+            test_true(Math.abs(measureEntry.duration - expectedDuration) <= testThreshold, measureEntryCommand +
+                      ".duration is approximately correct (up to " + testThreshold + "ms difference allowed)");
+        }
+    </script>
+    </head>
+    <body onload="onload_test();">
+        <h1>Description</h1>
+        <p>This test validates that the performance.measure() method is working properly when navigation timing
+           attributes are used in place of mark names. This test creates the following measures to test this method:
+            <ul>
+                <li>"measure_nav_start_no_end": created using a measure() call with a navigation timing attribute
+                    provided as the startMark and nothing provided as the endMark</li>
+                <li>"measure_nav_start_mark_end": created using a measure() call with a navigation timing attribute
+                    provided as the startMark and a mark name provided as the endMark</li>
+                <li>"measure_mark_start_nav_end": created using a measure() call with a mark name provided as the
+                    startMark and a navigation timing attribute provided as the endMark</li>
+                <li>"measure_nav_start_nav_end":created using a measure() call with a navigation timing attribute
+                    provided as both the startMark and endMark</li>
+            </ul>
+           After creating each measure, the existence of these measures is validated by calling
+           performance.getEntriesByName() with each measure name
+        </p>
+
+        <div id="log"></div>
+    </body>
+</html>
diff --git a/test/fixtures/wpt/user-timing/measure_syntax_err.any.js b/test/fixtures/wpt/user-timing/measure_syntax_err.any.js
new file mode 100644
index 00000000000000..9b762a40906351
--- /dev/null
+++ b/test/fixtures/wpt/user-timing/measure_syntax_err.any.js
@@ -0,0 +1,33 @@
+test(function () {
+   self.performance.mark("existing_mark");
+   var entries = self.performance.getEntriesByName("existing_mark");
+   assert_equals(entries.length, 1);
+   self.performance.measure("measure", "existing_mark");
+}, "Create a mark \"existing_mark\"");
+test(function () {
+   assert_throws_dom("SyntaxError", function () {
+       self.performance.measure("measure", "mark");
+   });
+}, "self.performance.measure(\"measure\", \"mark\"), where \"mark\" is a non-existent mark, " +
+                          "throws a SyntaxError exception.");
+
+test(function () {
+   assert_throws_dom("SyntaxError", function () {
+       self.performance.measure("measure", "mark", "existing_mark");
+   });
+}, "self.performance.measure(\"measure\", \"mark\", \"existing_mark\"), where \"mark\" is a " +
+                          "non-existent mark, throws a SyntaxError exception.");
+
+test(function () {
+   assert_throws_dom("SyntaxError", function () {
+       self.performance.measure("measure", "existing_mark", "mark");
+   });
+}, "self.performance.measure(\"measure\", \"existing_mark\", \"mark\"), where \"mark\" " +
+                            "is a non-existent mark, throws a SyntaxError exception.");
+
+test(function () {
+   assert_throws_dom("SyntaxError", function () {
+       self.performance.measure("measure", "mark", "mark");
+   });
+}, "self.performance.measure(\"measure\", \"mark\", \"mark\"), where \"mark\" is a " +
+                          "non-existent mark, throws a SyntaxError exception.");
diff --git a/test/fixtures/wpt/user-timing/measures.html b/test/fixtures/wpt/user-timing/measures.html
new file mode 100644
index 00000000000000..0de68965ddb9c7
--- /dev/null
+++ b/test/fixtures/wpt/user-timing/measures.html
@@ -0,0 +1,66 @@
+<!DOCTYPE html>
+<html>
+<head>
+<meta charset="utf-8" />
+<title>functionality test of window.performance.measure</title>
+<link rel="author" title="Intel" href="http://www.intel.com/" />
+<link rel="help" href="http://www.w3.org/TR/user-timing/#extensions-performance-interface"/>
+<script src="/resources/testharness.js"></script>
+<script src="/resources/testharnessreport.js"></script>
+<script src="/common/performance-timeline-utils.js"></script>
+<script src="resources/webperftestharness.js"></script>
+<script src="resources/webperftestharnessextension.js"></script>
+<script>
+setup({ explicit_done: true });
+
+function onload_test()
+{
+    const context = new PerformanceContext(window.performance);
+    const entrylist_checker = new performance_entrylist_checker('measure');
+    const measure_names = measures.map(function(x) {return x[0];});
+
+    test_equals(context.getEntriesByType('measure').length, 0, 'There should be ' + 0 + ' entries returned.');
+
+    mark_names.forEach(function(name) {
+        context.mark(name);
+    });
+    measures.forEach(context.initialMeasures, context);
+
+    let measure_entrylist = context.getEntriesByType('measure');
+    entrylist_checker.entrylist_check(measure_entrylist, measures.length, measure_names,
+        'Checking all entries.');
+
+    for (let i = 0; i < measure_entrylist.length; ++i)
+    {
+        const measure_entrylist_by_name = context.getEntriesByName(measure_entrylist[i].name, 'measure');
+        entrylist_checker.entrylist_check(measure_entrylist_by_name, 1, measure_names,
+            'First loop: checking entry of name "' + measure_entrylist[i].name + '".');
+    }
+
+    // Following cases test for scenarios that measure names are tied for two times
+    mark_names.forEach(function(name) {
+        context.mark(name);
+    });
+    measures.forEach(context.initialMeasures, context);
+
+    measure_entrylist = context.getEntriesByType('measure');
+    entrylist_checker.entrylist_check(measure_entrylist, measures.length * 2, measure_names,
+        'Checking all doubly measured entries.');
+
+    for (let i = 0; i < measure_entrylist.length; ++i)
+    {
+        const measure_entrylist_by_name = context.getEntriesByName(measure_entrylist[i].name, 'measure');
+        entrylist_checker.entrylist_check(measure_entrylist_by_name, 2, measure_names,
+            'Second loop step ' + i + ': checking entry of name "' + measure_entrylist[i].name + '".');
+    }
+
+    done();
+}
+</script>
+</head>
+<body onload=onload_test()>
+    <h1>Description</h1>
+    <p>This test validates functionality of the interface window.performance.measure.</p>
+    <div id="log"></div>
+</body>
+</html>
diff --git a/test/fixtures/wpt/user-timing/performance-measure-invalid.worker.js b/test/fixtures/wpt/user-timing/performance-measure-invalid.worker.js
new file mode 100644
index 00000000000000..29efb729992cc6
--- /dev/null
+++ b/test/fixtures/wpt/user-timing/performance-measure-invalid.worker.js
@@ -0,0 +1,9 @@
+importScripts("/resources/testharness.js");
+
+test(() => {
+  assert_throws_js(TypeError, () => {
+    performance.measure('name', 'navigationStart', 'navigationStart');
+  });
+}, "When converting 'navigationStart' to a timestamp, the global object has to be a Window object.");
+
+done();
diff --git a/test/fixtures/wpt/user-timing/resources/user-timing-helper.js b/test/fixtures/wpt/user-timing/resources/user-timing-helper.js
new file mode 100644
index 00000000000000..8d43768ec28196
--- /dev/null
+++ b/test/fixtures/wpt/user-timing/resources/user-timing-helper.js
@@ -0,0 +1,30 @@
+// Compares a list of performance entries to a predefined one.
+// actualEntries is an array of performance entries from the user agent,
+// and expectedEntries is an array of performance entries minted by the test.
+// The comparison doesn't assert the order of the entries.
+function checkEntries(actualEntries, expectedEntries) {
+  assert_equals(actualEntries.length, expectedEntries.length,
+      `The length of actual and expected entries should match.
+      actual: ${JSON.stringify(actualEntries)},
+      expected: ${JSON.stringify(expectedEntries)}`);
+  const actualEntrySet = new Set(actualEntries.map(ae=>ae.name));
+  assert_equals(actualEntrySet.size, actualEntries.length, `Actual entry names are not unique: ${JSON.stringify(actualEntries)}`);
+  const expectedEntrySet = new Set(expectedEntries.map(ee=>ee.name));
+  assert_equals(expectedEntrySet.size, expectedEntries.length, `Expected entry names are not unique: ${JSON.stringify(expectedEntries)}`);
+  actualEntries.forEach(ae=>{
+    const expectedEntry = expectedEntries.find(e=>e.name === ae.name);
+    assert_true(!!expectedEntry, `Entry name '${ae.name}' was not found.`);
+    checkEntry(ae, expectedEntry);
+  });
+}
+
+function checkEntry(entry, {name, entryType, startTime, detail, duration}) {
+  assert_equals(entry.name, name);
+  assert_equals(entry.entryType, entryType);
+  if (startTime !== undefined)
+    assert_equals(entry.startTime, startTime);
+  if (detail !== undefined)
+    assert_equals(JSON.stringify(entry.detail), JSON.stringify(detail));
+  if (duration !== undefined)
+    assert_equals(entry.duration, duration);
+}
diff --git a/test/fixtures/wpt/user-timing/resources/webperftestharness.js b/test/fixtures/wpt/user-timing/resources/webperftestharness.js
new file mode 100644
index 00000000000000..2fbd0210de906d
--- /dev/null
+++ b/test/fixtures/wpt/user-timing/resources/webperftestharness.js
@@ -0,0 +1,124 @@
+//
+// Helper functions for User Timing tests
+//
+
+var timingAttributes = [
+    "navigationStart",
+    "unloadEventStart",
+    "unloadEventEnd",
+    "redirectStart",
+    "redirectEnd",
+    "fetchStart",
+    "domainLookupStart",
+    "domainLookupEnd",
+    "connectStart",
+    "connectEnd",
+    "secureConnectionStart",
+    "requestStart",
+    "responseStart",
+    "responseEnd",
+    "domLoading",
+    "domInteractive",
+    "domContentLoadedEventStart",
+    "domContentLoadedEventEnd",
+    "domComplete",
+    "loadEventStart",
+    "loadEventEnd"
+];
+
+function has_required_interfaces()
+{
+    if (window.performance.mark == undefined ||
+        window.performance.clearMarks == undefined ||
+        window.performance.measure == undefined ||
+        window.performance.clearMeasures == undefined ||
+        window.performance.getEntriesByName == undefined ||
+        window.performance.getEntriesByType == undefined ||
+        window.performance.getEntries == undefined) {
+        return false;
+    }
+
+    return true;
+}
+
+function test_namespace(child_name, skip_root)
+{
+    if (skip_root === undefined) {
+        var msg = 'window.performance is defined';
+        wp_test(function () { assert_not_equals(performanceNamespace, undefined, msg); }, msg);
+    }
+
+    if (child_name !== undefined) {
+        var msg2 = 'window.performance.' + child_name + ' is defined';
+        wp_test(function() { assert_not_equals(performanceNamespace[child_name], undefined, msg2); }, msg2);
+    }
+}
+
+function test_attribute_exists(parent_name, attribute_name, properties)
+{
+    var msg = 'window.performance.' + parent_name + '.' + attribute_name + ' is defined.';
+    wp_test(function() { assert_not_equals(performanceNamespace[parent_name][attribute_name], undefined, msg); }, msg, properties);
+}
+
+function test_enum(parent_name, enum_name, value, properties)
+{
+    var msg = 'window.performance.' + parent_name + '.' + enum_name + ' is defined.';
+    wp_test(function() { assert_not_equals(performanceNamespace[parent_name][enum_name], undefined, msg); }, msg, properties);
+
+    msg = 'window.performance.' + parent_name + '.' + enum_name + ' = ' + value;
+    wp_test(function() { assert_equals(performanceNamespace[parent_name][enum_name], value, msg); }, msg, properties);
+}
+
+function test_timing_order(attribute_name, greater_than_attribute, properties)
+{
+    // ensure it's not 0 first
+    var msg = "window.performance.timing." + attribute_name + " > 0";
+    wp_test(function() { assert_true(performanceNamespace.timing[attribute_name] > 0, msg); }, msg, properties);
+
+    // ensure it's in the right order
+    msg = "window.performance.timing." + attribute_name + " >= window.performance.timing." + greater_than_attribute;
+    wp_test(function() { assert_true(performanceNamespace.timing[attribute_name] >= performanceNamespace.timing[greater_than_attribute], msg); }, msg, properties);
+}
+
+function test_timing_greater_than(attribute_name, greater_than, properties)
+{
+    var msg = "window.performance.timing." + attribute_name + " > " + greater_than;
+    test_greater_than(performanceNamespace.timing[attribute_name], greater_than, msg, properties);
+}
+
+function test_timing_equals(attribute_name, equals, msg, properties)
+{
+    var test_msg = msg || "window.performance.timing." + attribute_name + " == " + equals;
+    test_equals(performanceNamespace.timing[attribute_name], equals, test_msg, properties);
+}
+
+//
+// Non-test related helper functions
+//
+
+function sleep_milliseconds(n)
+{
+    var start = new Date().getTime();
+    while (true) {
+        if ((new Date().getTime() - start) >= n) break;
+    }
+}
+
+//
+// Common helper functions
+//
+
+function test_greater_than(value, greater_than, msg, properties)
+{
+    wp_test(function () { assert_true(value > greater_than, msg); }, msg, properties);
+}
+
+function test_greater_or_equals(value, greater_than, msg, properties)
+{
+    wp_test(function () { assert_true(value >= greater_than, msg); }, msg, properties);
+}
+
+function test_not_equals(value, notequals, msg, properties)
+{
+    wp_test(function() { assert_not_equals(value, notequals, msg); }, msg, properties);
+}
diff --git a/test/fixtures/wpt/user-timing/resources/webperftestharnessextension.js b/test/fixtures/wpt/user-timing/resources/webperftestharnessextension.js
new file mode 100644
index 00000000000000..8640918d4f255e
--- /dev/null
+++ b/test/fixtures/wpt/user-timing/resources/webperftestharnessextension.js
@@ -0,0 +1,202 @@
+//
+// Helper functions for User Timing tests
+//
+
+var mark_names = [
+    '',
+    '1',
+    'abc',
+];
+
+var measures = [
+    [''],
+    ['2', 1],
+    ['aaa', 'navigationStart', ''],
+];
+
+function test_method_exists(method, method_name, properties)
+{
+    var msg;
+    if (typeof method === 'function')
+        msg = 'performance.' + method.name + ' is supported!';
+    else
+        msg = 'performance.' + method_name + ' is supported!';
+    wp_test(function() { assert_equals(typeof method, 'function', msg); }, msg, properties);
+}
+
+function test_method_throw_exception(func_str, exception, msg)
+{
+    let exception_name;
+    let test_func;
+    if (typeof exception == "function") {
+        exception_name = exception.name;
+        test_func = assert_throws_js;
+    } else {
+        exception_name = exception;
+        test_func = assert_throws_dom;
+    }
+    var msg = 'Invocation of ' + func_str + ' should throw ' + exception_name  + ' Exception.';
+    wp_test(function() { test_func(exception, function() {eval(func_str)}, msg); }, msg);
+}
+
+function test_noless_than(value, greater_than, msg, properties)
+{
+    wp_test(function () { assert_true(value >= greater_than, msg); }, msg, properties);
+}
+
+function test_fail(msg, properties)
+{
+    wp_test(function() { assert_unreached(); }, msg, properties);
+}
+
+function test_resource_entries(entries, expected_entries)
+{
+    // This is slightly convoluted so that we can sort the output.
+    var actual_entries = {};
+    var origin = window.location.protocol + "//" + window.location.host;
+
+    for (var i = 0; i < entries.length; ++i) {
+        var entry = entries[i];
+        var found = false;
+        for (var expected_entry in expected_entries) {
+            if (entry.name == origin + expected_entry) {
+                found = true;
+                if (expected_entry in actual_entries) {
+                    test_fail(expected_entry + ' is not expected to have duplicate entries');
+                }
+                actual_entries[expected_entry] = entry;
+                break;
+            }
+        }
+        if (!found) {
+            test_fail(entries[i].name + ' is not expected to be in the Resource Timing buffer');
+        }
+    }
+
+    sorted_urls = [];
+    for (var i in actual_entries) {
+        sorted_urls.push(i);
+    }
+    sorted_urls.sort();
+    for (var i in sorted_urls) {
+        var url = sorted_urls[i];
+        test_equals(actual_entries[url].initiatorType,
+                    expected_entries[url],
+                    origin + url + ' is expected to have initiatorType ' + expected_entries[url]);
+    }
+    for (var j in expected_entries) {
+        if (!(j in actual_entries)) {
+            test_fail(origin + j + ' is expected to be in the Resource Timing buffer');
+        }
+    }
+}
+
+function performance_entrylist_checker(type)
+{
+    const entryType = type;
+
+    function entry_check(entry, expectedNames, testDescription = '')
+    {
+        const msg = testDescription + 'Entry \"' + entry.name + '\" should be one that we have set.';
+        wp_test(function() { assert_in_array(entry.name, expectedNames, msg); }, msg);
+        test_equals(entry.entryType, entryType, testDescription + 'entryType should be \"' + entryType + '\".');
+        if (type === "measure") {
+            test_true(isFinite(entry.startTime), testDescription + 'startTime should be a number.');
+            test_true(isFinite(entry.duration), testDescription + 'duration should be a number.');
+        } else if (type === "mark") {
+            test_greater_than(entry.startTime, 0, testDescription + 'startTime should greater than 0.');
+            test_equals(entry.duration, 0, testDescription + 'duration of mark should be 0.');
+        }
+    }
+
+    function entrylist_order_check(entryList)
+    {
+        let inOrder = true;
+        for (let i = 0; i < entryList.length - 1; ++i)
+        {
+            if (entryList[i + 1].startTime < entryList[i].startTime) {
+                inOrder = false;
+                break;
+            }
+        }
+        return inOrder;
+    }
+
+    function entrylist_check(entryList, expectedLength, expectedNames, testDescription = '')
+    {
+        test_equals(entryList.length, expectedLength, testDescription + 'There should be ' + expectedLength + ' entries.');
+        test_true(entrylist_order_check(entryList), testDescription + 'Entries in entrylist should be in order.');
+        for (let i = 0; i < entryList.length; ++i)
+        {
+            entry_check(entryList[i], expectedNames, testDescription + 'Entry_list ' + i + '. ');
+        }
+    }
+
+    return{"entrylist_check":entrylist_check};
+}
+
+function PerformanceContext(context)
+{
+    this.performanceContext = context;
+}
+
+PerformanceContext.prototype =
+{
+
+    initialMeasures: function(item, index, array)
+    {
+        this.performanceContext.measure.apply(this.performanceContext, item);
+    },
+
+    mark: function()
+    {
+        this.performanceContext.mark.apply(this.performanceContext, arguments);
+    },
+
+    measure: function()
+    {
+        this.performanceContext.measure.apply(this.performanceContext, arguments);
+    },
+
+    clearMarks: function()
+    {
+        this.performanceContext.clearMarks.apply(this.performanceContext, arguments);
+    },
+
+    clearMeasures: function()
+    {
+        this.performanceContext.clearMeasures.apply(this.performanceContext, arguments);
+
+    },
+
+    getEntries: function()
+    {
+        return this.performanceContext.getEntries.apply(this.performanceContext, arguments);
+    },
+
+    getEntriesByType: function()
+    {
+        return this.performanceContext.getEntriesByType.apply(this.performanceContext, arguments);
+    },
+
+    getEntriesByName: function()
+    {
+        return this.performanceContext.getEntriesByName.apply(this.performanceContext, arguments);
+    },
+
+    setResourceTimingBufferSize: function()
+    {
+        return this.performanceContext.setResourceTimingBufferSize.apply(this.performanceContext, arguments);
+    },
+
+    registerResourceTimingBufferFullCallback: function(func)
+    {
+        this.performanceContext.onresourcetimingbufferfull = func;
+    },
+
+    clearResourceTimings: function()
+    {
+        this.performanceContext.clearResourceTimings.apply(this.performanceContext, arguments);
+    }
+
+};
diff --git a/test/fixtures/wpt/user-timing/structured-serialize-detail.any.js b/test/fixtures/wpt/user-timing/structured-serialize-detail.any.js
new file mode 100644
index 00000000000000..78771b2f7663d4
--- /dev/null
+++ b/test/fixtures/wpt/user-timing/structured-serialize-detail.any.js
@@ -0,0 +1,64 @@
+test(function() {
+  performance.clearMarks();
+  const detail = { randomInfo: 123 }
+  const markEntry = new PerformanceMark("A", { detail });
+  assert_equals(markEntry.detail.randomInfo, detail.randomInfo);
+  assert_not_equals(markEntry.detail, detail);
+}, "The detail property in the mark constructor should be structured-clone.");
+
+test(function() {
+  performance.clearMarks();
+  const detail = { randomInfo: 123 }
+  const markEntry = performance.mark("A", { detail });
+  assert_not_equals(markEntry.detail, detail);
+}, "The detail property in the mark method should be structured-clone.");
+
+test(function() {
+  performance.clearMarks();
+  const markEntry = performance.mark("A");
+  assert_equals(markEntry.detail, null);
+}, "When accessing detail from a mark entry and the detail is not provided, just return a null value.");
+
+test(function() {
+  performance.clearMarks();
+  const detail = { unserializable: Symbol() };
+  assert_throws_dom("DataCloneError", ()=>{
+    new PerformanceMark("A", { detail });
+  }, "Trying to structured-serialize a Symbol.");
+}, "Mark: Throw an exception when the detail property cannot be structured-serialized.");
+
+test(function() {
+  performance.clearMeasures();
+  const detail = { randomInfo: 123 }
+  const measureEntry = performance.measure("A", { start: 0, detail });
+  assert_not_equals(measureEntry.detail, detail);
+}, "The detail property in the measure method should be structured-clone.");
+
+test(function() {
+  performance.clearMeasures();
+  const detail = { randomInfo: 123 }
+  const measureEntry = performance.measure("A", { start: 0, detail });
+  assert_equals(measureEntry.detail, measureEntry.detail);
+}, "The detail property in the measure method should be the same reference.");
+
+test(function() {
+  performance.clearMeasures();
+  const measureEntry = performance.measure("A");
+  assert_equals(measureEntry.detail, null);
+}, "When accessing detail from a measure entry and the detail is not provided, just return a null value.");
+
+test(function() {
+  performance.clearMeasures();
+  const detail = { unserializable: Symbol() };
+  assert_throws_dom("DataCloneError", ()=>{
+    performance.measure("A", { start: 0, detail });
+  }, "Trying to structured-serialize a Symbol.");
+}, "Measure: Throw an exception when the detail property cannot be structured-serialized.");
+
+test(function() {
+  const bar = { 1: 2 };
+  const detail = { foo: 1, bar };
+  const mark = performance.mark("m", { detail });
+  detail.foo = 2;
+  assert_equals(mark.detail.foo, 1);
+}, "The detail object is cloned when passed to mark API.");
diff --git a/test/fixtures/wpt/user-timing/supported-usertiming-types.any.js b/test/fixtures/wpt/user-timing/supported-usertiming-types.any.js
new file mode 100644
index 00000000000000..ea3b2fe9dc90f7
--- /dev/null
+++ b/test/fixtures/wpt/user-timing/supported-usertiming-types.any.js
@@ -0,0 +1,37 @@
+test(() => {
+  if (typeof PerformanceObserver.supportedEntryTypes === "undefined")
+    assert_unreached("supportedEntryTypes is not supported.");
+  const types = PerformanceObserver.supportedEntryTypes;
+  assert_true(types.includes("mark"),
+    "There should be 'mark' in PerformanceObserver.supportedEntryTypes");
+  assert_true(types.includes("measure"),
+    "There should be 'measure' in PerformanceObserver.supportedEntryTypes");
+  assert_greater_than(types.indexOf("measure"), types.indexOf('mark'),
+    "The 'measure' entry should appear after the 'mark' entry");
+}, "supportedEntryTypes contains 'mark' and 'measure'.");
+
+if (typeof PerformanceObserver.supportedEntryTypes !== "undefined") {
+  const entryTypes = {
+    "mark": () => {
+      performance.mark('foo');
+    },
+    "measure": () => {
+      performance.measure('bar');
+    }
+  }
+  for (let entryType in entryTypes) {
+    if (PerformanceObserver.supportedEntryTypes.includes(entryType)) {
+      promise_test(async() => {
+        await new Promise((resolve) => {
+          new PerformanceObserver(function (list, observer) {
+            observer.disconnect();
+            resolve();
+          }).observe({entryTypes: [entryType]});
+
+          // Force the PerformanceEntry.
+          entryTypes[entryType]();
+        })
+      }, `'${entryType}' entries should be observable.`)
+    }
+  }
+}
diff --git a/test/fixtures/wpt/user-timing/user-timing-tojson.html b/test/fixtures/wpt/user-timing/user-timing-tojson.html
new file mode 100644
index 00000000000000..6aef7fa904ab95
--- /dev/null
+++ b/test/fixtures/wpt/user-timing/user-timing-tojson.html
@@ -0,0 +1,44 @@
+<!doctype html>
+<html>
+<head>
+<script src="/resources/testharness.js"></script>
+<script src="/resources/testharnessreport.js"></script>
+</head>
+<body>
+<script>
+const keys = [
+  'name',
+  'entryType',
+  'startTime',
+  'duration',
+];
+test(() => {
+  performance.mark('a');
+  const markEntries = performance.getEntriesByType('mark');
+  assert_equals(1, markEntries.length);
+  const markEntry = markEntries[0];
+  assert_equals(markEntry.entryType, 'mark');
+  assert_equals(typeof(markEntry.toJSON), 'function');
+  const markJSON = markEntry.toJSON();
+  assert_equals(typeof(markJSON), 'object');
+  for (const key of keys) {
+    assert_equals(markJSON[key], markEntry[key], `PerformanceMark ${key} entry does not match its toJSON value`);
+  }
+}, 'Test toJSON() in PerformanceMark');
+
+test(() => {
+  performance.measure('m');
+  const measureEntries = performance.getEntriesByType('measure');
+  assert_equals(1, measureEntries.length);
+  const measureEntry = measureEntries[0];
+  assert_equals(measureEntry.entryType, 'measure');
+  assert_equals(typeof(measureEntry.toJSON), 'function');
+  const measureJSON = measureEntry.toJSON();
+  assert_equals(typeof(measureJSON), 'object');
+  for (const key of keys) {
+    assert_equals(measureJSON[key], measureEntry[key], `PerformanceMeasure ${key} entry does not match its toJSON value`);
+  }
+}, 'Test toJSON() in PerformanceMeasure');
+</script>
+</body>
+</html>
diff --git a/test/fixtures/wpt/user-timing/user_timing_exists.any.js b/test/fixtures/wpt/user-timing/user_timing_exists.any.js
new file mode 100644
index 00000000000000..adf9052ebd58d8
--- /dev/null
+++ b/test/fixtures/wpt/user-timing/user_timing_exists.any.js
@@ -0,0 +1,12 @@
+test(function() {
+    assert_not_equals(self.performance.mark, undefined);
+}, "self.performance.mark is defined.");
+test(function() {
+    assert_not_equals(self.performance.clearMarks, undefined);
+}, "self.performance.clearMarks is defined.");
+test(function() {
+    assert_not_equals(self.performance.measure, undefined);
+}, "self.performance.measure is defined.");
+test(function() {
+    assert_not_equals(self.performance.clearMeasures, undefined);
+}, "self.performance.clearMeasures is defined.");
diff --git a/test/fixtures/wpt/versions.json b/test/fixtures/wpt/versions.json
index fb10c7d403d730..fb49e36cc07747 100644
--- a/test/fixtures/wpt/versions.json
+++ b/test/fixtures/wpt/versions.json
@@ -36,9 +36,13 @@
     "path": "html/webappapis/timers"
   },
   "interfaces": {
-    "commit": "fcb671ed8b068b25cee87429d803833777f35c2c",
+    "commit": "80a417662387b6eda904607d78ad246c5d8bf191",
     "path": "interfaces"
   },
+  "performance-timeline": {
+    "commit": "17ebc3aea0d6321e69554067c39ab5855e6fb67e",
+    "path": "performance-timeline"
+  },
   "resources": {
     "commit": "972ca5b6693bffebebc5805e1b9da68a6876e1f6",
     "path": "resources"
@@ -50,5 +54,9 @@
   "url": {
     "commit": "77d54aa9e0405f737987b59331f3584e3e1c26f9",
     "path": "url"
+  },
+  "user-timing": {
+    "commit": "df24fb604e2d40528ac1d1b5dd970e32fc5c2978",
+    "path": "user-timing"
   }
 }
\ No newline at end of file
diff --git a/test/parallel/test-perf-hooks-usertiming.js b/test/parallel/test-perf-hooks-usertiming.js
index 401d0a6816481a..e7ef26889eae0f 100644
--- a/test/parallel/test-perf-hooks-usertiming.js
+++ b/test/parallel/test-perf-hooks-usertiming.js
@@ -29,7 +29,7 @@ assert(measure);
   assert.strictEqual(m.entryType, 'mark');
   assert.strictEqual(typeof m.startTime, 'number');
   assert.strictEqual(m.duration, 0);
-  assert.strictEqual(m.details, undefined);
+  assert.strictEqual(m.detail, null);
 });
 
 clearMarks();
@@ -38,11 +38,18 @@ assert.throws(() => mark(Symbol('a')), {
   message: /Cannot convert a Symbol value to a string/
 });
 
-[undefined, null, 1, 'any', {}, []].forEach((detail) => {
+[undefined, null].forEach((detail) => {
   const m = mark('a', { detail });
   assert.strictEqual(m.name, 'a');
   assert.strictEqual(m.entryType, 'mark');
-  assert.strictEqual(m.detail, detail);
+  assert.deepStrictEqual(m.detail, null);
+});
+[1, 'any', {}, []].forEach((detail) => {
+  const m = mark('a', { detail });
+  assert.strictEqual(m.name, 'a');
+  assert.strictEqual(m.entryType, 'mark');
+  // Value of detail is structured cloned.
+  assert.deepStrictEqual(m.detail, detail);
 });
 
 clearMarks();
diff --git a/test/wpt/status/performance-timeline.json b/test/wpt/status/performance-timeline.json
new file mode 100644
index 00000000000000..0967ef424bce67
--- /dev/null
+++ b/test/wpt/status/performance-timeline.json
@@ -0,0 +1 @@
+{}
diff --git a/test/wpt/status/user-timing.json b/test/wpt/status/user-timing.json
new file mode 100644
index 00000000000000..b1110e6a5e798d
--- /dev/null
+++ b/test/wpt/status/user-timing.json
@@ -0,0 +1,11 @@
+{
+  "invoke_with_timing_attributes.worker.js": {
+    "skip": "importScripts not supported"
+  },
+  "performance-measure-invalid.worker.js": {
+    "skip": "importScripts not supported"
+  },
+  "idlharness.any.js": {
+    "skip": "idlharness cannot recognize Node.js environment"
+  }
+}
diff --git a/test/wpt/test-performance-timeline.js b/test/wpt/test-performance-timeline.js
new file mode 100644
index 00000000000000..36d13297ba57cc
--- /dev/null
+++ b/test/wpt/test-performance-timeline.js
@@ -0,0 +1,27 @@
+'use strict';
+require('../common');
+const { WPTRunner } = require('../common/wpt');
+
+const runner = new WPTRunner('user-timing');
+
+// Needed to access to DOMException.
+runner.setFlags(['--expose-internals']);
+
+runner.setInitScript(`
+  const {
+    PerformanceMark,
+    PerformanceMeasure,
+    PerformanceObserver,
+    performance,
+  } = require('perf_hooks');
+  global.PerformanceMark = performance;
+  global.PerformanceMeasure = performance;
+  global.PerformanceObserver = PerformanceObserver;
+  global.performance = performance;
+
+  const { internalBinding } = require('internal/test/binding');
+  const { DOMException } = internalBinding('messaging');
+  global.DOMException = DOMException;
+`);
+
+runner.runJsTests();
diff --git a/test/wpt/test-user-timing.js b/test/wpt/test-user-timing.js
new file mode 100644
index 00000000000000..36d13297ba57cc
--- /dev/null
+++ b/test/wpt/test-user-timing.js
@@ -0,0 +1,27 @@
+'use strict';
+require('../common');
+const { WPTRunner } = require('../common/wpt');
+
+const runner = new WPTRunner('user-timing');
+
+// Needed to access to DOMException.
+runner.setFlags(['--expose-internals']);
+
+runner.setInitScript(`
+  const {
+    PerformanceMark,
+    PerformanceMeasure,
+    PerformanceObserver,
+    performance,
+  } = require('perf_hooks');
+  global.PerformanceMark = performance;
+  global.PerformanceMeasure = performance;
+  global.PerformanceObserver = PerformanceObserver;
+  global.performance = performance;
+
+  const { internalBinding } = require('internal/test/binding');
+  const { DOMException } = internalBinding('messaging');
+  global.DOMException = DOMException;
+`);
+
+runner.runJsTests();