DevTools: add extension API to contribute trace events to timeline

third_party/WebKit/Source/devtools/front_end/timeline/CountersGraph.js

 /*
  * Copyright (C) 2012 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 206 matching lines @@
     this.draw();
     this._refreshCurrentValues();
   }
 
   /**
    * @override
    */
   refreshRecords() {
   }
 
+  /**
+   * @override
+   */
+  extensionDataAdded() {
+  }
+
   _clear() {
     var ctx = this._canvas.getContext('2d');
     ctx.clearRect(0, 0, ctx.canvas.width, ctx.canvas.height);
   }
 
   /**
    * @override
    * @param {?SDK.TracingModel.Event} event
    * @param {string=} regex
    * @param {boolean=} select
@@ skipping 350 matching lines @@
   /**
    * @override
    * @return {number}
    */
   boundarySpan() {
     return this._maximumBoundary - this._minimumBoundary;
   }
 };
 
 Timeline.CounterGraphCalculator._minWidth = 5;