[DevTools] Add power profiler and power overview in timeline panel.

Source/devtools/front_end/TimelineOverviewPane.js

 /*
  * Copyright (C) 2013 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 337 matching lines @@
 WebInspector.TimelineOverviewBase.prototype = {
     update: function()
     {
         this.resetCanvas();
     },
 
     reset: function()
     {
     },
 
+    timelineStarted: function() { },
+    timelineStopped: function() { },
+
     /**
      * @param {number} windowLeft
      * @param {number} windowRight
      * @return {!{startTime: number, endTime: number}}
      */
     windowTimes: function(windowLeft, windowRight)
     {
         var absoluteMin = this._model.minimumRecordTime();
         var timeSpan = this._model.maximumRecordTime() - absoluteMin;
         return {
@@ skipping 19 matching lines @@
     },
 
     resetCanvas: function()
     {
         this._canvas.width = this.element.clientWidth * window.devicePixelRatio;
         this._canvas.height = this.element.clientHeight * window.devicePixelRatio;
     },
 
     __proto__: WebInspector.VBox.prototype
 }