From da71dfeb54f9a8e2fe92c8113d853bf0723d457a Mon Sep 17 00:00:00 2001
From: Steven Orvell <sorvell@google.com>
Date: Thu, 5 Nov 2015 13:08:33 -0800
Subject: [PATCH] For efficiency, use cached events in data system, for
 property and path changes.

---
 src/lib/bind/accessors.html   | 14 +++-----------
 src/standard/notify-path.html |  5 ++++-
 src/standard/utils.html       | 32 ++++++++++++++++++++++++++------
 3 files changed, 33 insertions(+), 18 deletions(-)

diff --git a/src/lib/bind/accessors.html b/src/lib/bind/accessors.html
index 4704c2b41e..bb078b3ff1 100644
--- a/src/lib/bind/accessors.html
+++ b/src/lib/bind/accessors.html
@@ -21,17 +21,9 @@
     _modelApi: {
 
       _notifyChange: function(event, value) {
-        var cache = Polymer.Bind._dataEventCache;
-        var e = cache[event];
-        if (e) {
-          cache[event] = null;
-        } else {
-          e = new CustomEvent(event, 
-            {bubbles: false, cancelable: false, detail: {}});
-        } 
-        e.detail.value = value;
-        this.dispatchEvent(e);
-        cache[event] = e;
+        // use a cached event here (_useCache: true) for efficiency
+        this.fire(event, {value: value}, 
+          {bubbles: false, cancelable: false, _useCache: true});
       },
 
       // TODO(sjmiles): removing _notifyListener from here breaks accessors.html
diff --git a/src/standard/notify-path.html b/src/standard/notify-path.html
index 354dc37a00..927f8403d4 100644
--- a/src/standard/notify-path.html
+++ b/src/standard/notify-path.html
@@ -380,10 +380,11 @@
         var rootName = this._modelForPath(path);
         var dashCaseName = Polymer.CaseMap.camelToDashCase(rootName);
         var eventName = dashCaseName + this._EVENT_CHANGED;
+        // use a cached event here (_useCache: true) for efficiency
         this.fire(eventName, {
           path: path,
           value: value
-        }, {bubbles: false});
+        }, {bubbles: false, _useCache: true});
       },
 
       _modelForPath: function(path) {
@@ -602,6 +603,8 @@
       prepareModelNotifyPath: function(model) {
         this.mixin(model, {
           fire: Polymer.Base.fire,
+          _getEvent: Polymer.Base._getEvent,
+          __eventCache: Polymer.Base.__eventCache,
           notifyPath: Polymer.Base.notifyPath,
           _get: Polymer.Base._get,
           _EVENT_CHANGED: Polymer.Base._EVENT_CHANGED,
diff --git a/src/standard/utils.html b/src/standard/utils.html
index f4241f4fb0..93c5368254 100644
--- a/src/standard/utils.html
+++ b/src/standard/utils.html
@@ -198,6 +198,7 @@
       });
     },
 
+    
     /**
      * Dispatches a custom event with an optional detail value.
      *
@@ -214,18 +215,37 @@
     fire: function(type, detail, options) {
       options = options || Polymer.nob;
       var node = options.node || this;
-      var detail = (detail === null || detail === undefined) ? Polymer.nob : detail;
+      var detail = (detail === null || detail === undefined) ? {} : detail;
       var bubbles = options.bubbles === undefined ? true : options.bubbles;
       var cancelable = Boolean(options.cancelable);
-      var event = new CustomEvent(type, {
-        bubbles: Boolean(bubbles),
-        cancelable: cancelable,
-        detail: detail
-      });
+      var useCache = options._useCache;
+      var event = this._getEvent(type, bubbles, cancelable, useCache);
+      event.detail = detail;
+      if (useCache) {
+        this.__eventCache[type] = null;
+      }
       node.dispatchEvent(event);
+      if (useCache) {
+        this.__eventCache[type] = event;
+      }
       return event;
     },
 
+    __eventCache: {},
+
+    _getEvent: function(type, bubbles, cancelable, useCache) {
+      var event = useCache && this.__eventCache[type];
+      if (!event || ((event.bubbles != bubbles) || 
+          (event.cancelable != cancelable))) {
+        event = new Event(type, {
+          bubbles: Boolean(bubbles),
+          cancelable: cancelable
+        });
+      }
+      return event;
+    },
+
+
     /**
      * Runs a callback function asyncronously.
      *