diff --git a/types/lib/elements/array-selector.d.ts b/types/lib/elements/array-selector.d.ts
index 81ffc584e3..9a66af0e99 100644
--- a/types/lib/elements/array-selector.d.ts
+++ b/types/lib/elements/array-selector.d.ts
@@ -37,33 +37,33 @@ declare namespace Polymer {
     /**
      * An array containing items from which selection will be made.
      */
-    items: any[]|null;
+    items: any[]|null|undefined;
 
     /**
      * When `true`, multiple items may be selected at once (in this case,
      * `selected` is an array of currently selected items).  When `false`,
      * only one item may be selected at a time.
      */
-    multi: boolean;
+    multi: boolean|null|undefined;
 
     /**
      * When `multi` is true, this is an array that contains any selected.
      * When `multi` is false, this is the currently selected item, or `null`
      * if no item is selected.
      */
-    selected: Object|Object[]|null;
+    selected: object|object[]|null;
 
     /**
      * When `multi` is false, this is the currently selected item, or `null`
      * if no item is selected.
      */
-    selectedItem: Object|null;
+    selectedItem: object|null;
 
     /**
      * When `true`, calling `select` on an item that is already selected
      * will deselect the item.
      */
-    toggle: boolean;
+    toggle: boolean|null|undefined;
 
     /**
      * Clears the selection state.
diff --git a/types/lib/elements/dom-if.d.ts b/types/lib/elements/dom-if.d.ts
index 67fd3c9a0e..7507dbee39 100644
--- a/types/lib/elements/dom-if.d.ts
+++ b/types/lib/elements/dom-if.d.ts
@@ -35,7 +35,7 @@ declare namespace Polymer {
     /**
      * A boolean indicating whether this template should stamp.
      */
-    if: boolean;
+    if: boolean|null|undefined;
 
     /**
      * When true, elements will be removed from DOM and discarded when `if`
@@ -44,7 +44,7 @@ declare namespace Polymer {
      * in the DOM when `if` becomes false, which is generally results
      * in better performance.
      */
-    restamp: boolean;
+    restamp: boolean|null|undefined;
     connectedCallback(): any;
     disconnectedCallback(): any;
 
diff --git a/types/lib/elements/dom-module.d.ts b/types/lib/elements/dom-module.d.ts
index dabea1711e..bbeccc111b 100644
--- a/types/lib/elements/dom-module.d.ts
+++ b/types/lib/elements/dom-module.d.ts
@@ -33,7 +33,13 @@ declare namespace Polymer {
    *     let img = customElements.get('dom-module').import('foo', 'img');
    */
   class DomModule extends HTMLElement {
-    attributeChangedCallback(name: string, old: any, value: any): void;
+
+    /**
+     * @param name Name of attribute.
+     * @param old Old value of attribute.
+     * @param value Current value of attribute.
+     */
+    attributeChangedCallback(name: string, old: string|null, value: string|null): void;
 
     /**
      * Registers the dom-module at a given id. This method should only be called
diff --git a/types/lib/elements/dom-repeat.d.ts b/types/lib/elements/dom-repeat.d.ts
index abbbe04823..723c074c3c 100644
--- a/types/lib/elements/dom-repeat.d.ts
+++ b/types/lib/elements/dom-repeat.d.ts
@@ -111,13 +111,13 @@ declare namespace Polymer {
      * An array containing items determining how many instances of the template
      * to stamp and that that each template instance should bind to.
      */
-    items: any[]|null;
+    items: any[]|null|undefined;
 
     /**
      * The name of the variable to add to the binding scope for the array
      * element associated with a given template instance.
      */
-    as: string;
+    as: string|null|undefined;
 
     /**
      * The name of the variable to add to the binding scope with the index
@@ -125,7 +125,7 @@ declare namespace Polymer {
      * Note, for the index in the `this.items` array, use the value of the
      * `itemsIndexAs` property.
      */
-    indexAs: string;
+    indexAs: string|null|undefined;
 
     /**
      * The name of the variable to add to the binding scope with the index
@@ -133,7 +133,7 @@ declare namespace Polymer {
      * this instance in the sorted and filtered list of rendered items,
      * use the value of the `indexAs` property.
      */
-    itemsIndexAs: string;
+    itemsIndexAs: string|null|undefined;
 
     /**
      * A function that should determine the sort order of the items.  This
@@ -142,7 +142,7 @@ declare namespace Polymer {
      * function should match the sort function passed to `Array.sort`.
      * Using a sort function has no effect on the underlying `items` array.
      */
-    sort: Function|null;
+    sort: Function|null|undefined;
 
     /**
      * A function that can be used to filter items out of the view.  This
@@ -151,7 +151,7 @@ declare namespace Polymer {
      * function should match the sort function passed to `Array.filter`.
      * Using a filter function has no effect on the underlying `items` array.
      */
-    filter: Function|null;
+    filter: Function|null|undefined;
 
     /**
      * When using a `filter` or `sort` function, the `observe` property
@@ -160,7 +160,7 @@ declare namespace Polymer {
      * These should generally be fields of `item` that the sort or filter
      * function depends on.
      */
-    observe: string;
+    observe: string|null|undefined;
 
     /**
      * When using a `filter` or `sort` function, the `delay` property
@@ -169,14 +169,14 @@ declare namespace Polymer {
      * This is useful in rate-limiting shuffling of the view when
      * item changes may be frequent.
      */
-    delay: number;
+    delay: number|null|undefined;
 
     /**
      * Count of currently rendered items after `filter` (if any) has been applied.
      * If "chunking mode" is enabled, `renderedItemCount` is updated each time a
      * set of template instances is rendered.
      */
-    renderedItemCount: number;
+    renderedItemCount: number|null|undefined;
 
     /**
      * Defines an initial count of template instances to render after setting
@@ -185,7 +185,7 @@ declare namespace Polymer {
      * incrementally at each animation frame therof until all instances have
      * been rendered.
      */
-    initialCount: number;
+    initialCount: number|null|undefined;
 
     /**
      * When `initialCount` is used, this property defines a frame rate (in
@@ -199,8 +199,8 @@ declare namespace Polymer {
      * throughput for event handlers and other tasks, but results in a
      * longer time for the remaining items to complete rendering.
      */
-    targetFramerate: number;
-    _targetFrameTime: number;
+    targetFramerate: number|null|undefined;
+    _targetFrameTime: number|null|undefined;
     disconnectedCallback(): any;
     connectedCallback(): any;
 
diff --git a/types/lib/legacy/class.d.ts b/types/lib/legacy/class.d.ts
index d84880e22b..832e025dce 100644
--- a/types/lib/legacy/class.d.ts
+++ b/types/lib/legacy/class.d.ts
@@ -23,7 +23,7 @@ declare namespace Polymer {
    * @returns Returns a new Element class extended by the
    * passed in `behaviors` and also by `Polymer.LegacyElementMixin`.
    */
-  function mixinBehaviors(behaviors: Object|any[]|null, klass: HTMLElement|{new(): HTMLElement}): {new(): HTMLElement};
+  function mixinBehaviors(behaviors: object|any[]|null, klass: HTMLElement|{new(): HTMLElement}): {new(): HTMLElement};
 
 
   /**
diff --git a/types/lib/legacy/legacy-element-mixin.d.ts b/types/lib/legacy/legacy-element-mixin.d.ts
index d834010aa5..70c69e317f 100644
--- a/types/lib/legacy/legacy-element-mixin.d.ts
+++ b/types/lib/legacy/legacy-element-mixin.d.ts
@@ -34,14 +34,10 @@ declare namespace Polymer {
     _debouncers: any;
 
     /**
-     * Provides an override implementation of `attributeChangedCallback`
-     * which adds the Polymer legacy API's `attributeChanged` method.
-     *
-     * @param name Name of attribute.
-     * @param old Old value of attribute.
-     * @param value Current value of attribute.
+     * Overrides the default `Polymer.PropertyEffects` implementation to
+     * add support for installing `hostAttributes` and `listeners`.
      */
-    attributeChangedCallback(name: string, old: string|null, value: string|null): void;
+    ready(): any;
 
     /**
      * Overrides the default `Polymer.PropertyEffects` implementation to
@@ -51,10 +47,14 @@ declare namespace Polymer {
     _initializeProperties(): any;
 
     /**
-     * Overrides the default `Polymer.PropertyEffects` implementation to
-     * add support for installing `hostAttributes` and `listeners`.
+     * Provides an override implementation of `attributeChangedCallback`
+     * which adds the Polymer legacy API's `attributeChanged` method.
+     *
+     * @param name Name of attribute.
+     * @param old Old value of attribute.
+     * @param value Current value of attribute.
      */
-    ready(): any;
+    attributeChangedCallback(name: string, old: string|null, value: string|null): void;
 
     /**
      * Provides an implementation of `connectedCallback`
@@ -187,7 +187,7 @@ declare namespace Polymer {
      * @param api Source object to copy properties from.
      * @returns prototype object that was passed as first argument.
      */
-    extend(prototype: Object|null, api: Object|null): Object|null;
+    extend(prototype: object|null, api: object|null): object|null;
 
     /**
      * Copies props from a source object to a target object.
@@ -200,7 +200,7 @@ declare namespace Polymer {
      * @param source Source object to copy properties from.
      * @returns Target object that was passed as first argument.
      */
-    mixin(target: Object|null, source: Object|null): Object|null;
+    mixin(target: object|null, source: object|null): object|null;
 
     /**
      * Sets the prototype of an object.
@@ -214,7 +214,7 @@ declare namespace Polymer {
      * @returns Returns the given `object` with its prototype set
      * to the given `prototype` object.
      */
-    chainObject(object: Object|null, prototype: Object|null): Object|null;
+    chainObject(object: object|null, prototype: object|null): object|null;
 
     /**
      * Calls `importNode` on the `content` of the `template` specified and
@@ -435,7 +435,7 @@ declare namespace Polymer {
      * `flush()` immediately invokes the debounced callback if the debouncer
      * is active.
      */
-    debounce(jobName: string, callback: () => void, wait: number): Object|null;
+    debounce(jobName: string, callback: () => void, wait: number): object|null;
 
     /**
      * Returns whether a named debouncer is active.
@@ -489,7 +489,7 @@ declare namespace Polymer {
      *    instance.
      * @returns Newly created and configured element.
      */
-    create(tag: string, props: Object|null): Element|null;
+    create(tag: string, props: object|null): Element|null;
 
     /**
      * Convenience method for importing an HTML document imperatively.
diff --git a/types/lib/legacy/mutable-data-behavior.d.ts b/types/lib/legacy/mutable-data-behavior.d.ts
index fad6fa58b4..67c7f5d50e 100644
--- a/types/lib/legacy/mutable-data-behavior.d.ts
+++ b/types/lib/legacy/mutable-data-behavior.d.ts
@@ -108,7 +108,7 @@ declare namespace Polymer {
      * for this element.  When true, Objects and Arrays will skip dirty
      * checking, otherwise strict equality checking will be used.
      */
-    mutableData: boolean;
+    mutableData: boolean|null|undefined;
 
     /**
      * Overrides `Polymer.PropertyEffects` to skip strict equality checking
diff --git a/types/lib/legacy/polymer.dom.d.ts b/types/lib/legacy/polymer.dom.d.ts
index e06dfaf5b3..49465a50b0 100644
--- a/types/lib/legacy/polymer.dom.d.ts
+++ b/types/lib/legacy/polymer.dom.d.ts
@@ -32,7 +32,7 @@ declare namespace Polymer {
      *
      * @returns True if node matched selector
      */
-    function matchesSelector(node: Element, selector: string): boolean;
+    function matchesSelector(node: Node, selector: string): boolean;
   }
 
   /**
diff --git a/types/lib/legacy/templatizer-behavior.d.ts b/types/lib/legacy/templatizer-behavior.d.ts
index b59cacd0f4..412a5b9609 100644
--- a/types/lib/legacy/templatizer-behavior.d.ts
+++ b/types/lib/legacy/templatizer-behavior.d.ts
@@ -97,7 +97,7 @@ declare namespace Polymer {
      * @returns Returns the created instance of
      * the template prepared by `templatize`.
      */
-    stamp(model?: Object|null): TemplateInstanceBase|null;
+    stamp(model?: object|null): TemplateInstanceBase|null;
 
     /**
      * Returns the template "model" (`TemplateInstance`) associated with
diff --git a/types/lib/mixins/element-mixin.d.ts b/types/lib/mixins/element-mixin.d.ts
index 91e243428f..d6e4bb76ee 100644
--- a/types/lib/mixins/element-mixin.d.ts
+++ b/types/lib/mixins/element-mixin.d.ts
@@ -11,11 +11,11 @@
 /// <reference path="../utils/boot.d.ts" />
 /// <reference path="../utils/settings.d.ts" />
 /// <reference path="../utils/mixin.d.ts" />
-/// <reference path="../utils/case-map.d.ts" />
 /// <reference path="../utils/style-gather.d.ts" />
 /// <reference path="../utils/resolve-url.d.ts" />
 /// <reference path="../elements/dom-module.d.ts" />
 /// <reference path="property-effects.d.ts" />
+/// <reference path="properties-mixin.d.ts" />
 
 declare namespace Polymer {
 
@@ -76,7 +76,7 @@ declare namespace Polymer {
    *   of dash-cased attributes based on `properties`)
    */
   function ElementMixin<T extends new(...args: any[]) => {}>(base: T): {
-    new(...args: any[]): ElementMixin & Polymer.PropertyEffects
+    new(...args: any[]): ElementMixin & Polymer.PropertyEffects & Polymer.PropertiesMixin
   } & T
 
   interface ElementMixin {
@@ -88,19 +88,9 @@ declare namespace Polymer {
     $: any;
 
     /**
-     * Provides a default implementation of the standard Custom Elements
-     * `attributeChangedCallback`.
-     *
-     * By default, attributes declared in `properties` metadata are
-     * deserialized using their `type` information to properties of the
-     * same name.  "Dash-cased" attributes are deserialized to "camelCase"
-     * properties.
-     *
-     * @param name Name of attribute.
-     * @param old Old value of attribute.
-     * @param value Current value of attribute.
+     * Stamps the element template.
      */
-    attributeChangedCallback(name: string, old: string|null, value: string|null): any;
+    ready(): any;
 
     /**
      * Overrides the default `Polymer.PropertyAccessors` to ensure class
@@ -112,11 +102,6 @@ declare namespace Polymer {
      */
     _initializeProperties(): any;
 
-    /**
-     * Stamps the element template.
-     */
-    ready(): any;
-
     /**
      * Implements `PropertyEffects`'s `_readyClients` call. Attaches
      * element dom by calling `_attachDom` with the dom stamped from the
@@ -136,12 +121,6 @@ declare namespace Polymer {
      */
     connectedCallback(): any;
 
-    /**
-     * Provides a default implementation of the standard Custom Elements
-     * `disconnectedCallback`.
-     */
-    disconnectedCallback(): any;
-
     /**
      * Attaches an element's stamped dom to itself. By default,
      * this method creates a `shadowRoot` and adds the dom to it.
@@ -169,7 +148,7 @@ declare namespace Polymer {
      * @param properties Bag of custom property key/values to
      *   apply to this element.
      */
-    updateStyles(properties?: Object|null): void;
+    updateStyles(properties?: object|null): void;
 
     /**
      * Rewrites a given URL relative to a base URL. The base URL defaults to
diff --git a/types/lib/mixins/mutable-data.d.ts b/types/lib/mixins/mutable-data.d.ts
index 9c01002076..6788d46d94 100644
--- a/types/lib/mixins/mutable-data.d.ts
+++ b/types/lib/mixins/mutable-data.d.ts
@@ -117,7 +117,7 @@ declare namespace Polymer {
      * for this element.  When true, Objects and Arrays will skip dirty
      * checking, otherwise strict equality checking will be used.
      */
-    mutableData: boolean;
+    mutableData: boolean|null|undefined;
 
     /**
      * Overrides `Polymer.PropertyEffects` to provide option for skipping
diff --git a/types/lib/mixins/properties-changed.d.ts b/types/lib/mixins/properties-changed.d.ts
new file mode 100644
index 0000000000..4dabca1f14
--- /dev/null
+++ b/types/lib/mixins/properties-changed.d.ts
@@ -0,0 +1,257 @@
+/**
+ * DO NOT EDIT
+ *
+ * This file was automatically generated by
+ *   https://github.com/Polymer/gen-typescript-declarations
+ *
+ * To modify these typings, edit the source file(s):
+ *   lib/mixins/properties-changed.html
+ */
+
+/// <reference path="../utils/boot.d.ts" />
+/// <reference path="../utils/mixin.d.ts" />
+/// <reference path="../utils/async.d.ts" />
+
+declare namespace Polymer {
+
+  /**
+   * Element class mixin that provides basic meta-programming for creating one
+   * or more property accessors (getter/setter pair) that enqueue an async
+   * (batched) `_propertiesChanged` callback.
+   *
+   * For basic usage of this mixin, simply declare attributes to observe via
+   * the standard `static get observedAttributes()`, implement `_propertiesChanged`
+   * on the class, and then call `MyClass.createPropertiesForAttributes()` once
+   * on the class to generate property accessors for each observed attribute
+   * prior to instancing. Last, call `this._enableProperties()` in the element's
+   * `connectedCallback` to enable the accessors.
+   *
+   * Any `observedAttributes` will automatically be
+   * deserialized via `attributeChangedCallback` and set to the associated
+   * property using `dash-case`-to-`camelCase` convention.
+   */
+  function PropertiesChanged<T extends new(...args: any[]) => {}>(base: T): {
+    new(...args: any[]): PropertiesChanged
+  } & T
+
+  interface PropertiesChanged {
+
+    /**
+     * Creates a setter/getter pair for the named property with its own
+     * local storage.  The getter returns the value in the local storage,
+     * and the setter calls `_setProperty`, which updates the local storage
+     * for the property and enqueues a `_propertiesChanged` callback.
+     *
+     * This method may be called on a prototype or an instance.  Calling
+     * this method may overwrite a property value that already exists on
+     * the prototype/instance by creating the accessor.
+     *
+     * @param property Name of the property
+     * @param readOnly When true, no setter is created; the
+     *   protected `_setProperty` function must be used to set the property
+     */
+    _createPropertyAccessor(property: string, readOnly?: boolean): any;
+
+    /**
+     * Defines a property accessor for the given property.
+     *
+     * @param property Name of the property
+     * @param readOnly When true, no setter is created
+     */
+    _definePropertyAccessor(property: string, readOnly?: boolean): any;
+
+    /**
+     * Lifecycle callback called when properties are enabled via
+     * `_enableProperties`.
+     *
+     * Users may override this function to implement behavior that is
+     * dependent on the element having its property data initialized, e.g.
+     * from defaults (initialized from `constructor`, `_initializeProperties`),
+     * `attributeChangedCallback`, or values propagated from host e.g. via
+     * bindings.  `super.ready()` must be called to ensure the data system
+     * becomes enabled.
+     */
+    ready(): any;
+
+    /**
+     * Initializes the local storage for property accessors.
+     *
+     * Provided as an override point for performing any setup work prior
+     * to initializing the property accessor system.
+     */
+    _initializeProperties(): any;
+
+    /**
+     * Called at ready time with bag of instance properties that overwrote
+     * accessors when the element upgraded.
+     *
+     * The default implementation sets these properties back into the
+     * setter at ready time.  This method is provided as an override
+     * point for customizing or providing more efficient initialization.
+     *
+     * @param props Bag of property values that were overwritten
+     *   when creating property accessors.
+     */
+    _initializeInstanceProperties(props: object|null): any;
+
+    /**
+     * Updates the local storage for a property (via `_setPendingProperty`)
+     * and enqueues a `_proeprtiesChanged` callback.
+     *
+     * @param property Name of the property
+     * @param value Value to set
+     */
+    _setProperty(property: string, value: any): any;
+
+    /**
+     * Returns the value for the given property.
+     *
+     * @param property Name of property
+     * @returns Value for the given property
+     */
+    _getProperty(property: string): any;
+
+    /**
+     * Updates the local storage for a property, records the previous value,
+     * and adds it to the set of "pending changes" that will be passed to the
+     * `_propertiesChanged` callback.  This method does not enqueue the
+     * `_propertiesChanged` callback.
+     *
+     * @param property Name of the property
+     * @param value Value to set
+     * @param ext Not used here; affordance for closure
+     * @returns Returns true if the property changed
+     */
+    _setPendingProperty(property: string, value: any, ext?: boolean): boolean;
+
+    /**
+     * Marks the properties as invalid, and enqueues an async
+     * `_propertiesChanged` callback.
+     */
+    _invalidateProperties(): any;
+
+    /**
+     * Call to enable property accessor processing. Before this method is
+     * called accessor values will be set but side effects are
+     * queued. When called, any pending side effects occur immediately.
+     * For elements, generally `connectedCallback` is a normal spot to do so.
+     * It is safe to call this method multiple times as it only turns on
+     * property accessors once.
+     */
+    _enableProperties(): any;
+
+    /**
+     * Calls the `_propertiesChanged` callback with the current set of
+     * pending changes (and old values recorded when pending changes were
+     * set), and resets the pending set of changes. Generally, this method
+     * should not be called in user code.
+     */
+    _flushProperties(): any;
+
+    /**
+     * Callback called when any properties with accessors created via
+     * `_createPropertyAccessor` have been set.
+     *
+     * @param currentProps Bag of all current accessor values
+     * @param changedProps Bag of properties changed since the last
+     *   call to `_propertiesChanged`
+     * @param oldProps Bag of previous values for each property
+     *   in `changedProps`
+     */
+    _propertiesChanged(currentProps: object, changedProps: object, oldProps: object): any;
+
+    /**
+     * Method called to determine whether a property value should be
+     * considered as a change and cause the `_propertiesChanged` callback
+     * to be enqueued.
+     *
+     * The default implementation returns `true` for primitive types if a
+     * strict equality check fails, and returns `true` for all Object/Arrays.
+     * The method always returns false for `NaN`.
+     *
+     * Override this method to e.g. provide stricter checking for
+     * Objects/Arrays when using immutable patterns.
+     *
+     * @param property Property name
+     * @param value New property value
+     * @param old Previous property value
+     * @returns Whether the property should be considered a change
+     *   and enqueue a `_proeprtiesChanged` callback
+     */
+    _shouldPropertyChange(property: string, value: any, old: any): boolean;
+
+    /**
+     * Implements native Custom Elements `attributeChangedCallback` to
+     * set an attribute value to a property via `_attributeToProperty`.
+     *
+     * @param name Name of attribute that changed
+     * @param old Old attribute value
+     * @param value New attribute value
+     */
+    attributeChangedCallback(name: string, old: string|null, value: string|null): any;
+
+    /**
+     * Deserializes an attribute to its associated property.
+     *
+     * This method calls the `_deserializeValue` method to convert the string to
+     * a typed value.
+     *
+     * @param attribute Name of attribute to deserialize.
+     * @param value of the attribute.
+     * @param type type to deserialize to, defaults to the value
+     * returned from `typeForProperty`
+     */
+    _attributeToProperty(attribute: string, value: string|null, type?: any): any;
+
+    /**
+     * Serializes a property to its associated attribute.
+     *
+     * @param property Property name to reflect.
+     * @param attribute Attribute name to reflect to.
+     * @param value Property value to refect.
+     */
+    _propertyToAttribute(property: string, attribute?: string, value?: any): any;
+
+    /**
+     * Sets a typed value to an HTML attribute on a node.
+     *
+     * This method calls the `_serializeValue` method to convert the typed
+     * value to a string.  If the `_serializeValue` method returns `undefined`,
+     * the attribute will be removed (this is the default for boolean
+     * type `false`).
+     *
+     * @param node Element to set attribute to.
+     * @param value Value to serialize.
+     * @param attribute Attribute name to serialize to.
+     */
+    _valueToNodeAttribute(node: Element|null, value: any, attribute: string): any;
+
+    /**
+     * Converts a typed JavaScript value to a string.
+     *
+     * This method is called by Polymer when setting JS property values to
+     * HTML attributes.  Users may override this method on Polymer element
+     * prototypes to provide serialization for custom types.
+     *
+     * @param value Property value to serialize.
+     * @returns String serialized from the provided
+     * property  value.
+     */
+    _serializeValue(value: any): string|undefined;
+
+    /**
+     * Converts a string to a typed JavaScript value.
+     *
+     * This method is called when reading HTML attribute values to
+     * JS properties.  Users may override this method to provide
+     * deserialization for custom `type`s. The given `type` is executed
+     * as a function with the value as an argument. The `Boolean` `type`
+     * is specially handled such that an empty string returns true.
+     *
+     * @param value Value to deserialize.
+     * @param type Type to deserialize the string to.
+     * @returns Typed value deserialized from the provided string.
+     */
+    _deserializeValue(value: string|null, type?: any): any;
+  }
+}
diff --git a/types/lib/mixins/properties-mixin.d.ts b/types/lib/mixins/properties-mixin.d.ts
new file mode 100644
index 0000000000..d31e89cd3b
--- /dev/null
+++ b/types/lib/mixins/properties-mixin.d.ts
@@ -0,0 +1,52 @@
+/**
+ * DO NOT EDIT
+ *
+ * This file was automatically generated by
+ *   https://github.com/Polymer/gen-typescript-declarations
+ *
+ * To modify these typings, edit the source file(s):
+ *   lib/mixins/properties-mixin.html
+ */
+
+/// <reference path="../utils/boot.d.ts" />
+/// <reference path="../utils/mixin.d.ts" />
+/// <reference path="properties-changed.d.ts" />
+
+declare namespace Polymer {
+
+  /**
+   * Mixin that provides a minimal starting point to using the PropertiesChanged
+   * mixin by providing a mechanism to declare properties in a static
+   * getter (e.g. static get properties() { return { foo: String } }). Changes
+   * are reported via the `_propertiesChanged` method.
+   *
+   * This mixin provides no specific support for rendering. Users are expected
+   * to create a ShadowRoot and put content into it and update it in whatever
+   * way makes sense. This can be done in reaction to properties changing by
+   * implementing `_propertiesChanged`.
+   */
+  function PropertiesMixin<T extends new(...args: any[]) => {}>(base: T): {
+    new(...args: any[]): PropertiesMixin & Polymer.PropertiesChanged
+  } & T
+
+  interface PropertiesMixin {
+
+    /**
+     * Overrides `PropertiesChanged` method and adds a call to
+     * `finalize` which lazily configures the element's property accessors.
+     */
+    _initializeProperties(): any;
+
+    /**
+     * Called when the element is added to a document.
+     * Calls `_enableProperties` to turn on property system from
+     * `PropertiesChanged`.
+     */
+    connectedCallback(): any;
+
+    /**
+     * Called when the element is removed from a document
+     */
+    disconnectedCallback(): any;
+  }
+}
diff --git a/types/lib/mixins/property-accessors.d.ts b/types/lib/mixins/property-accessors.d.ts
index a62eabc39e..c0db6b965a 100644
--- a/types/lib/mixins/property-accessors.d.ts
+++ b/types/lib/mixins/property-accessors.d.ts
@@ -11,7 +11,7 @@
 /// <reference path="../utils/boot.d.ts" />
 /// <reference path="../utils/mixin.d.ts" />
 /// <reference path="../utils/case-map.d.ts" />
-/// <reference path="../utils/async.d.ts" />
+/// <reference path="properties-changed.d.ts" />
 
 declare namespace Polymer {
 
@@ -32,105 +32,36 @@ declare namespace Polymer {
    * property using `dash-case`-to-`camelCase` convention.
    */
   function PropertyAccessors<T extends new(...args: any[]) => {}>(base: T): {
-    new(...args: any[]): PropertyAccessors
+    new(...args: any[]): PropertyAccessors & Polymer.PropertiesChanged
   } & T
 
   interface PropertyAccessors {
 
     /**
-     * Implements native Custom Elements `attributeChangedCallback` to
-     * set an attribute value to a property via `_attributeToProperty`.
+     * Overrides PropertiesChanged implementation to save existing prototype
+     * property value so that it can be reset.
      *
-     * @param name Name of attribute that changed
-     * @param old Old attribute value
-     * @param value New attribute value
-     */
-    attributeChangedCallback(name: string, old: string|null, value: string|null): any;
-
-    /**
-     * Initializes the local storage for property accessors.
-     *
-     * Provided as an override point for performing any setup work prior
-     * to initializing the property accessor system.
-     */
-    _initializeProperties(): void;
-
-    /**
-     * Called at instance time with bag of properties that were overwritten
-     * by accessors on the prototype when accessors were created.
-     *
-     * The default implementation sets these properties back into the
-     * setter at instance time.  This method is provided as an override
-     * point for customizing or providing more efficient initialization.
-     *
-     * @param props Bag of property values that were overwritten
-     *   when creating property accessors.
-     */
-    _initializeProtoProperties(props: Object|null): void;
-
-    /**
-     * Called at ready time with bag of instance properties that overwrote
-     * accessors when the element upgraded.
-     *
-     * The default implementation sets these properties back into the
-     * setter at ready time.  This method is provided as an override
-     * point for customizing or providing more efficient initialization.
-     *
-     * @param props Bag of property values that were overwritten
-     *   when creating property accessors.
-     */
-    _initializeInstanceProperties(props: Object|null): void;
-
-    /**
-     * Ensures the element has the given attribute. If it does not,
-     * assigns the given value to the attribute.
-     *
-     * @param attribute Name of attribute to ensure is set.
-     * @param value of the attribute.
-     */
-    _ensureAttribute(attribute: string, value: string): void;
-
-    /**
-     * Deserializes an attribute to its associated property.
-     *
-     * This method calls the `_deserializeValue` method to convert the string to
-     * a typed value.
+     * @param property Name of the property
+     * @param readOnly When true, no setter is created
      *
-     * @param attribute Name of attribute to deserialize.
-     * @param value of the attribute.
-     * @param type type to deserialize to.
+     * When calling on a prototype, any overwritten values are saved in
+     * `__dataProto`, and it is up to the subclasser to decide how/when
+     * to set those properties back into the accessor.  When calling on an
+     * instance, the overwritten value is set via `_setPendingProperty`,
+     * and the user should call `_invalidateProperties` or `_flushProperties`
+     * for the values to take effect.
      */
-    _attributeToProperty(attribute: string, value: string|null, type?: any): void;
+    _definePropertyAccessor(property: string, readOnly?: boolean): void;
 
     /**
-     * Serializes a property to its associated attribute.
-     *
-     * @param property Property name to reflect.
-     * @param attribute Attribute name to reflect.
-     * @param value Property value to refect.
+     * Overrides PropertiesChanged implementation to initialize values for
+     * accessors created for values that already existed on the element
+     * prototype.
      */
-    _propertyToAttribute(property: string, attribute?: string, value?: any): void;
-
-    /**
-     * Sets a typed value to an HTML attribute on a node.
-     *
-     * This method calls the `_serializeValue` method to convert the typed
-     * value to a string.  If the `_serializeValue` method returns `undefined`,
-     * the attribute will be removed (this is the default for boolean
-     * type `false`).
-     *
-     * @param node Element to set attribute to.
-     * @param value Value to serialize.
-     * @param attribute Attribute name to serialize to.
-     */
-    _valueToNodeAttribute(node: Element|null, value: any, attribute: string): void;
+    _initializeProperties(): void;
 
     /**
-     * Converts a typed JavaScript value to a string.
-     *
-     * This method is called by Polymer when setting JS property values to
-     * HTML attributes.  Users may override this method on Polymer element
-     * prototypes to provide serialization for custom types.
+     * Overrides PropertiesChanged implemention to serialize objects as JSON.
      *
      * @param value Property value to serialize.
      * @returns String serialized from the provided property value.
@@ -147,9 +78,6 @@ declare namespace Polymer {
      * `properties` configuration object for a given property, and is
      * by convention the constructor for the type to deserialize.
      *
-     * Note: The return value of `undefined` is used as a sentinel value to
-     * indicate the attribute should be removed.
-     *
      * @param value Attribute value to deserialize.
      * @param type Type to deserialize the string to.
      * @returns Typed value deserialized from the provided string.
@@ -157,55 +85,34 @@ declare namespace Polymer {
     _deserializeValue(value: string|null, type?: any): any;
 
     /**
-     * Creates a setter/getter pair for the named property with its own
-     * local storage.  The getter returns the value in the local storage,
-     * and the setter calls `_setProperty`, which updates the local storage
-     * for the property and enqueues a `_propertiesChanged` callback.
-     *
-     * This method may be called on a prototype or an instance.  Calling
-     * this method may overwrite a property value that already exists on
-     * the prototype/instance by creating the accessor.  When calling on
-     * a prototype, any overwritten values are saved in `__dataProto`,
-     * and it is up to the subclasser to decide how/when to set those
-     * properties back into the accessor.  When calling on an instance,
-     * the overwritten value is set via `_setPendingProperty`, and the
-     * user should call `_invalidateProperties` or `_flushProperties`
-     * for the values to take effect.
+     * Called at instance time with bag of properties that were overwritten
+     * by accessors on the prototype when accessors were created.
      *
-     * @param property Name of the property
-     * @param readOnly When true, no setter is created; the
-     *   protected `_setProperty` function must be used to set the property
-     */
-    _createPropertyAccessor(property: string, readOnly?: boolean): void;
-
-    /**
-     * Returns true if this library created an accessor for the given property.
+     * The default implementation sets these properties back into the
+     * setter at instance time.  This method is provided as an override
+     * point for customizing or providing more efficient initialization.
      *
-     * @param property Property name
-     * @returns True if an accessor was created
+     * @param props Bag of property values that were overwritten
+     *   when creating property accessors.
      */
-    _hasAccessor(property: string): boolean;
+    _initializeProtoProperties(props: object|null): void;
 
     /**
-     * Updates the local storage for a property (via `_setPendingProperty`)
-     * and enqueues a `_propertiesChanged` callback.
+     * Ensures the element has the given attribute. If it does not,
+     * assigns the given value to the attribute.
      *
-     * @param property Name of the property
-     * @param value Value to set
+     * @param attribute Name of attribute to ensure is set.
+     * @param value of the attribute.
      */
-    _setProperty(property: string, value: any): void;
+    _ensureAttribute(attribute: string, value: string): void;
 
     /**
-     * Updates the local storage for a property, records the previous value,
-     * and adds it to the set of "pending changes" that will be passed to the
-     * `_propertiesChanged` callback.  This method does not enqueue the
-     * `_propertiesChanged` callback.
+     * Returns true if this library created an accessor for the given property.
      *
-     * @param property Name of the property
-     * @param value Value to set
-     * @returns Returns true if the property changed
+     * @param property Property name
+     * @returns True if an accessor was created
      */
-    _setPendingProperty(property: string, value: any): boolean;
+    _hasAccessor(property: string): boolean;
 
     /**
      * Returns true if the specified property has a pending change.
@@ -214,75 +121,5 @@ declare namespace Polymer {
      * @returns True if property has a pending change
      */
     _isPropertyPending(prop: string): boolean;
-
-    /**
-     * Marks the properties as invalid, and enqueues an async
-     * `_propertiesChanged` callback.
-     */
-    _invalidateProperties(): void;
-
-    /**
-     * Call to enable property accessor processing. Before this method is
-     * called accessor values will be set but side effects are
-     * queued. When called, any pending side effects occur immediately.
-     * For elements, generally `connectedCallback` is a normal spot to do so.
-     * It is safe to call this method multiple times as it only turns on
-     * property accessors once.
-     */
-    _enableProperties(): void;
-
-    /**
-     * Calls the `_propertiesChanged` callback with the current set of
-     * pending changes (and old values recorded when pending changes were
-     * set), and resets the pending set of changes. Generally, this method
-     * should not be called in user code.
-     */
-    _flushProperties(): void;
-
-    /**
-     * Lifecycle callback called the first time properties are being flushed.
-     * Prior to `ready`, all property sets through accessors are queued and
-     * their effects are flushed after this method returns.
-     *
-     * Users may override this function to implement behavior that is
-     * dependent on the element having its properties initialized, e.g.
-     * from defaults (initialized from `constructor`, `_initializeProperties`),
-     * `attributeChangedCallback`, or values propagated from host e.g. via
-     * bindings.  `super.ready()` must be called to ensure the data system
-     * becomes enabled.
-     */
-    ready(): any;
-
-    /**
-     * Callback called when any properties with accessors created via
-     * `_createPropertyAccessor` have been set.
-     *
-     * @param currentProps Bag of all current accessor values
-     * @param changedProps Bag of properties changed since the last
-     *   call to `_propertiesChanged`
-     * @param oldProps Bag of previous values for each property
-     *   in `changedProps`
-     */
-    _propertiesChanged(currentProps: Object, changedProps: Object, oldProps: Object): any;
-
-    /**
-     * Method called to determine whether a property value should be
-     * considered as a change and cause the `_propertiesChanged` callback
-     * to be enqueued.
-     *
-     * The default implementation returns `true` for primitive types if a
-     * strict equality check fails, and returns `true` for all Object/Arrays.
-     * The method always returns false for `NaN`.
-     *
-     * Override this method to e.g. provide stricter checking for
-     * Objects/Arrays when using immutable patterns.
-     *
-     * @param property Property name
-     * @param value New property value
-     * @param old Previous property value
-     * @returns Whether the property should be considered a change
-     *   and enqueue a `_propertiesChanged` callback
-     */
-    _shouldPropertyChange(property: string, value: any, old: any): boolean;
   }
 }
diff --git a/types/lib/mixins/property-effects.d.ts b/types/lib/mixins/property-effects.d.ts
index c4a8d856f4..191ae6fb5d 100644
--- a/types/lib/mixins/property-effects.d.ts
+++ b/types/lib/mixins/property-effects.d.ts
@@ -70,16 +70,15 @@ declare namespace Polymer {
      * @returns Cloned template content
      */
     _stampTemplate(template: HTMLTemplateElement): StampedTemplate;
-    _initializeProperties(): any;
 
     /**
-     * Overrides `Polymer.PropertyAccessors` implementation to provide a
-     * more efficient implementation of initializing properties from
-     * the prototype on the instance.
-     *
-     * @param props Properties to initialize on the prototype
+     * Overrides `PropertyAccessors` so that property accessor
+     * side effects are not enabled until after client dom is fully ready.
+     * Also calls `_flushClients` callback to ensure client dom is enabled
+     * that was not enabled as a result of flushing properties.
      */
-    _initializeProtoProperties(props: Object|null): any;
+    ready(): any;
+    _initializeProperties(): any;
 
     /**
      * Overrides `Polymer.PropertyAccessors` implementation to avoid setting
@@ -87,7 +86,7 @@ declare namespace Polymer {
      *
      * @param props Properties to initialize on the instance
      */
-    _initializeInstanceProperties(props: Object|null): any;
+    _initializeInstanceProperties(props: object|null): any;
 
     /**
      * Overrides base implementation to ensure all accessors set `shouldNotify`
@@ -96,7 +95,7 @@ declare namespace Polymer {
     _setProperty(property: any, value: any): any;
 
     /**
-     * Overrides the `PropertyAccessors` implementation to introduce special
+     * Overrides the `PropertiesChanged` implementation to introduce special
      * dirty check logic depending on the property & value being set:
      *
      * 1. Any value set to a path (e.g. 'obj.prop': 42 or 'obj.prop': {...})
@@ -140,12 +139,9 @@ declare namespace Polymer {
     _invalidateProperties(): any;
 
     /**
-     * Overrides `PropertyAccessors` so that property accessor
-     * side effects are not enabled until after client dom is fully ready.
-     * Also calls `_flushClients` callback to ensure client dom is enabled
-     * that was not enabled as a result of flushing properties.
+     * Overrides superclass implementation.
      */
-    ready(): any;
+    _flushProperties(): any;
 
     /**
      * Implements `PropertyAccessors`'s properties changed callback.
@@ -155,6 +151,15 @@ declare namespace Polymer {
      */
     _propertiesChanged(currentProps: any, changedProps: any, oldProps: any): any;
 
+    /**
+     * Overrides `Polymer.PropertyAccessors` implementation to provide a
+     * more efficient implementation of initializing properties from
+     * the prototype on the instance.
+     *
+     * @param props Properties to initialize on the prototype
+     */
+    _initializeProtoProperties(props: object|null): any;
+
     /**
      * Equivalent to static `addPropertyEffect` API but can be called on
      * an instance to add effects at runtime.  See that method for
@@ -164,7 +169,7 @@ declare namespace Polymer {
      * @param type Effect type, from this.PROPERTY_EFFECT_TYPES
      * @param effect Effect metadata object
      */
-    _addPropertyEffect(property: string, type: string, effect?: Object|null): void;
+    _addPropertyEffect(property: string, type: string, effect?: object|null): void;
 
     /**
      * Removes the given property effect.
@@ -173,7 +178,7 @@ declare namespace Polymer {
      * @param type Effect type, from this.PROPERTY_EFFECT_TYPES
      * @param effect Effect metadata object to remove
      */
-    _removePropertyEffect(property: string, type: string, effect?: Object|null): void;
+    _removePropertyEffect(property: string, type: string, effect?: object|null): void;
 
     /**
      * Returns whether the current prototype/instance has a property effect
@@ -278,7 +283,7 @@ declare namespace Polymer {
      *
      * @param client PropertyEffects client to enqueue
      */
-    _enqueueClient(client: Object|null): void;
+    _enqueueClient(client: object|null): void;
 
     /**
      * Flushes any clients previously enqueued via `_enqueueClient`, causing
@@ -306,7 +311,7 @@ declare namespace Polymer {
      *   `props` will be set. By default, `setProperties` will not set
      *   `readOnly: true` root properties.
      */
-    setProperties(props: Object|null, setReadOnly?: boolean): void;
+    setProperties(props: object|null, setReadOnly?: boolean): void;
 
     /**
      * Called to propagate any property changes to stamped template nodes
@@ -316,7 +321,7 @@ declare namespace Polymer {
      * @param oldProps Bag of previous values for changed properties
      * @param hasPaths True with `props` contains one or more paths
      */
-    _propagatePropertyChanges(changedProps: Object|null, oldProps: Object|null, hasPaths: boolean): void;
+    _propagatePropertyChanges(changedProps: object|null, oldProps: object|null, hasPaths: boolean): void;
 
     /**
      * Aliases one data path as another, such that path notifications from one
@@ -385,7 +390,7 @@ declare namespace Polymer {
      * @returns Value at the path, or `undefined` if any part of the path
      *   is undefined.
      */
-    get(path: string|Array<string|number>, root?: Object|null): any;
+    get(path: string|Array<string|number>, root?: object|null): any;
 
     /**
      * Convenience method for setting a value to a path and notifying any
@@ -406,7 +411,7 @@ declare namespace Polymer {
      * @param root Root object from which the path is evaluated.
      *   When specified, no notification will occur.
      */
-    set(path: string|Array<string|number>, value: any, root?: Object|null): void;
+    set(path: string|Array<string|number>, value: any, root?: object|null): void;
 
     /**
      * Adds items onto the end of the array at the path specified.
@@ -529,7 +534,7 @@ declare namespace Polymer {
      * @param dynamicFn Boolean or object map indicating
      *   whether method names should be included as a dependency to the effect.
      */
-    _createMethodObserver(expression: string, dynamicFn?: boolean|Object|null): void;
+    _createMethodObserver(expression: string, dynamicFn?: boolean|object|null): void;
 
     /**
      * Equivalent to static `createNotifyingProperty` API but can be called on
@@ -559,7 +564,7 @@ declare namespace Polymer {
      * @param dynamicFn Boolean or object map indicating
      *   whether method names should be included as a dependency to the effect.
      */
-    _createComputedProperty(property: string, expression: string, dynamicFn?: boolean|Object|null): void;
+    _createComputedProperty(property: string, expression: string, dynamicFn?: boolean|object|null): void;
 
     /**
      * Equivalent to static `bindTemplate` API but can be called on
diff --git a/types/lib/utils/async.d.ts b/types/lib/utils/async.d.ts
index bcc3a083e7..963d85af52 100644
--- a/types/lib/utils/async.d.ts
+++ b/types/lib/utils/async.d.ts
@@ -32,7 +32,7 @@ declare namespace Polymer {
        *
        * @returns An async timeout interface
        */
-      function after(delay: number): AsyncInterface;
+      function after(delay?: number): AsyncInterface;
 
 
       /**
@@ -40,7 +40,15 @@ declare namespace Polymer {
        *
        * @returns Handle used for canceling task
        */
-      function run(fn: Function): number;
+      function run(fn: Function, delay?: number): number;
+
+
+      /**
+       * Enqueues a function called in the next task.
+       *
+       * @returns Handle used for canceling task
+       */
+      function run(fn: Function, delay?: number): number;
 
 
       /**
@@ -50,7 +58,7 @@ declare namespace Polymer {
 
 
       /**
-       * Cancels a previously enqueued `animationFrame` callback.
+       * Cancels a previously enqueued `timeOut` callback.
        */
       function cancel(handle: number): void;
     }
@@ -66,7 +74,27 @@ declare namespace Polymer {
        *
        * @returns Handle used for canceling task
        */
-      function run(fn: Function): number;
+      function run(fn: (p0: number) => any): number;
+
+
+      /**
+       * Enqueues a function called at `requestAnimationFrame` timing.
+       *
+       * @returns Handle used for canceling task
+       */
+      function run(fn: (p0: number) => any): number;
+
+
+      /**
+       * Cancels a previously enqueued `animationFrame` callback.
+       */
+      function cancel(handle: number): void;
+
+
+      /**
+       * Cancels a previously enqueued `animationFrame` callback.
+       */
+      function cancel(handle: number): void;
     }
 
     /**
diff --git a/types/lib/utils/flattened-nodes-observer.d.ts b/types/lib/utils/flattened-nodes-observer.d.ts
index 7c3324b84f..e6f5d2ed25 100644
--- a/types/lib/utils/flattened-nodes-observer.d.ts
+++ b/types/lib/utils/flattened-nodes-observer.d.ts
@@ -53,9 +53,6 @@ declare namespace Polymer {
    * ```
    */
   class FlattenedNodesObserver {
-    _shadyChildrenObserver: MutationObserver|null;
-    _nativeChildrenObserver: MutationObserver|null;
-    _boundSchedule: () => any;
 
     /**
      * Activates an observer. This method is automatically called when
diff --git a/types/lib/utils/html-tag.d.ts b/types/lib/utils/html-tag.d.ts
index 2a706b55a4..a3c879554c 100644
--- a/types/lib/utils/html-tag.d.ts
+++ b/types/lib/utils/html-tag.d.ts
@@ -37,5 +37,5 @@ declare namespace Polymer {
    *
    * @returns Constructed HTMLTemplateElement
    */
-  function html(strings: string[], ...values: any[]): HTMLTemplateElement;
+  function html(strings: ITemplateArray|null, ...values: any[]): HTMLTemplateElement;
 }
diff --git a/types/lib/utils/path.d.ts b/types/lib/utils/path.d.ts
index 0231991faa..afcc5efbac 100644
--- a/types/lib/utils/path.d.ts
+++ b/types/lib/utils/path.d.ts
@@ -137,7 +137,7 @@ declare namespace Polymer {
      * @returns Value at path, or `undefined` if the path could not be
      *  fully dereferenced.
      */
-    function get(root: Object|null, path: string|Array<string|number>, info?: Object|null): any;
+    function get(root: object|null, path: string|Array<string|number>, info?: object|null): any;
 
 
     /**
@@ -146,6 +146,6 @@ declare namespace Polymer {
      *
      * @returns The normalized version of the input path
      */
-    function set(root: Object|null, path: string|Array<string|number>, value: any): string|undefined;
+    function set(root: object|null, path: string|Array<string|number>, value: any): string|undefined;
   }
 }
diff --git a/types/lib/utils/templatize.d.ts b/types/lib/utils/templatize.d.ts
index 077893d00a..dc866ad9cf 100644
--- a/types/lib/utils/templatize.d.ts
+++ b/types/lib/utils/templatize.d.ts
@@ -113,7 +113,7 @@ declare namespace Polymer {
      * @returns Generated class bound to the template
      *   provided
      */
-    function templatize(template: HTMLTemplateElement, owner: Polymer_PropertyEffects, options?: Object|null): {new(): TemplateInstanceBase};
+    function templatize(template: HTMLTemplateElement, owner: Polymer_PropertyEffects, options?: object|null): {new(): TemplateInstanceBase};
 
 
     /**