Support counter graphs in Timeline based on trace events

Source/devtools/front_end/timeline/TimelineModelImpl.js

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 /**
  * @constructor
  * @extends {WebInspector.TimelineModel}
  * @param {!WebInspector.TimelineManager} timelineManager
  */
 WebInspector.TimelineModelImpl = function(timelineManager)
@@ skipping 464 matching lines @@
      * @return {string}
      */
     type: function()
     {
         return this._record.type;
     },
 
     /**
      * @return {?Object}
      */
+    counters: function()
+    {
+        return this.type() === WebInspector.TimelineModel.RecordType.UpdateCounters ? this.data() : null;
+    },
+
+    /**
+     * @return {?Object}
+     */
     highlightQuad: function()
     {
         var quad = null;
         var recordTypes = WebInspector.TimelineModel.RecordType;
         switch(this.type()) {
         case recordTypes.Layout:
             quad = this.data().root;
             break;
         case recordTypes.Paint:
             quad = this.data().clip;
@@ skipping 275 matching lines @@
                 break;
             length += itemLength;
             data.push(item);
             ++this._recordIndex;
         }
         if (this._recordIndex === this._payloads.length)
             data.push(data.pop() + "]");
         stream.write(data.join(separator), this._writeNextChunk.bind(this));
     }
 }