FlameChart: make flame chart vertically draggable.

Source/devtools/front_end/FlameChart.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 336 matching lines @@
 
     /**
      * @param {!MouseEvent} event
      */
     _startCanvasDragging: function(event)
     {
         if (!this._timelineData())
             return false;
         this._isDragging = true;
         this._maxDragOffset = 0;
-        this._dragStartPoint = event.pageX;
+        this._dragStartPointX = event.pageX;
+        this._dragStartPointY = event.pageY;
+        this._dragStartScrollTop = this._vScrollElement.scrollTop;
         this._dragStartWindowLeft = this._timeWindowLeft;
         this._dragStartWindowRight = this._timeWindowRight;
         this._canvas.style.cursor = "";
 
         return true;
     },
 
     /**
      * @param {!MouseEvent} event
      */
     _canvasDragging: function(event)
     {
-        var pixelShift = this._dragStartPoint - event.pageX;
+        var pixelShift = this._dragStartPointX - event.pageX;
+        var pixelScroll = this._dragStartPointY - event.pageY;
+        this._vScrollElement.scrollTop = this._dragStartScrollTop + pixelScroll;
         var windowShift = pixelShift / this._totalPixels;
         var windowTime = this._windowWidth * this._totalTime;
         var timeShift = windowTime * pixelShift / this._pixelWindowWidth;
         timeShift = Number.constrain(
             timeShift,
             this._zeroTime - this._dragStartWindowLeft,
             this._zeroTime + this._totalTime - this._dragStartWindowRight
         );
         var windowLeft = this._dragStartWindowLeft + timeShift;
         var windowRight = this._dragStartWindowRight + timeShift;
@@ skipping 424 matching lines @@
     reset: function()
     {
         this._highlightedEntryIndex = -1;
         this._selectedEntryIndex = -1;
         this._textWidth = {};
         this.update();
     },
 
     __proto__: WebInspector.HBox.prototype
 }