DevTools: Fix timeline overview window selection

Source/devtools/front_end/OverviewGrid.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 234 matching lines @@
     },
 
     /**
      * @param {!Event} event
      * @return {boolean}
      */
     _startWindowSelectorDragging: function(event)
     {
         if (!this._enabled)
             return false;
-        this._offsetLeft = event.pageX - event.offsetX;
-        var position = event.pageX - this._offsetLeft;
+        this._offsetLeft = this._parentElement.totalOffsetLeft();
+        var position = event.x - this._offsetLeft;
         this._overviewWindowSelector = new WebInspector.OverviewGrid.WindowSelector(this._parentElement, position);
         return true;
     },
 
     /**
      * @param {!Event} event
      */
     _windowSelectorDragging: function(event)
     {
-        this._overviewWindowSelector._updatePosition(event.pageX - this._offsetLeft);
+        this._overviewWindowSelector._updatePosition(event.x - this._offsetLeft);
         event.preventDefault();
     },
 
     /**
      * @param {!Event} event
      */
     _endWindowSelectorDragging: function(event)
     {
-        var window = this._overviewWindowSelector._close(event.pageX - this._offsetLeft);
+        var window = this._overviewWindowSelector._close(event.x - this._offsetLeft);
         delete this._overviewWindowSelector;
         if (window.end === window.start) { // Click, not drag.
             var middle = window.end;
             window.start = Math.max(0, middle - WebInspector.OverviewGrid.MinSelectableSize / 2);
             window.end = Math.min(this._parentElement.clientWidth, middle + WebInspector.OverviewGrid.MinSelectableSize / 2);
         } else if (window.end - window.start < WebInspector.OverviewGrid.MinSelectableSize) {
             if (this._parentElement.clientWidth - window.end > WebInspector.OverviewGrid.MinSelectableSize)
                 window.end = window.start + WebInspector.OverviewGrid.MinSelectableSize;
             else
                 window.start = window.end - WebInspector.OverviewGrid.MinSelectableSize;
@@ skipping 185 matching lines @@
         position = Math.max(0, Math.min(position, this._width));
         if (position < this._startPosition) {
             this._windowSelector.style.left = position + "px";
             this._windowSelector.style.right = this._width - this._startPosition + "px";
         } else {
             this._windowSelector.style.left = this._startPosition + "px";
             this._windowSelector.style.right = this._width - position + "px";
         }
     }
 }