DevTools: Bring back split view animation on show/hide sidebar button click.

Source/devtools/front_end/SplitView.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:
  *
  * 1. Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *
@@ skipping 800 matching lines @@
         this._updateShowHideSidebarButton();
 
         /**
          * @this {WebInspector.SplitView}
          * @param {!WebInspector.Event} event
          */
         function buttonClicked(event)
         {
             var show = this._isShowingOne;
             if (show)
-                this.showBoth();
+                this.showBoth(true);
             else
-                this.hideSidebar();
+                this.hideSidebar(true);
         }
 
         return this._showHideSidebarButton;
     },
 
     _updateShowHideSidebarButton: function()
     {
         if (!this._showHideSidebarButton)
             return;
         this._showHideSidebarButton.state = this._isShowingOne === this.isSidebarSecond() ? "left" : "right";
         this._showHideSidebarButton.title = this._isShowingOne ? WebInspector.UIString("Show %s", this._showHideSidebarButtonTitle) : WebInspector.UIString("Hide %s", this._showHideSidebarButtonTitle);
     },
 
     __proto__: WebInspector.View.prototype
 }