DevTools: fix author shadow dom inspection mode, speacial-case ua. Fix crash from the bug.

Source/devtools/front_end/ScreencastView.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 705 matching lines @@
     _viewportDimensions: function()
     {
         const gutterSize = 30;
         const bordersSize = WebInspector.ScreencastView._bordersSize;
         return { width: this.element.offsetWidth - bordersSize - gutterSize,
                  height: this.element.offsetHeight - bordersSize - gutterSize - WebInspector.ScreencastView._navBarHeight};
     },
 
     /**
      * @param {boolean} enabled
-     * @param {boolean} inspectShadowDOM
+     * @param {boolean} inspectUAShadowDOM
      * @param {!DOMAgent.HighlightConfig} config
      * @param {function(?Protocol.Error)=} callback
      */
-    setInspectModeEnabled: function(enabled, inspectShadowDOM, config, callback)
+    setInspectModeEnabled: function(enabled, inspectUAShadowDOM, config, callback)
     {
         this._inspectModeConfig = enabled ? config : null;
         if (callback)
             callback(null);
     },
 
     /**
      * @param {!CanvasRenderingContext2D} context
      */
     _createCheckerboardPattern: function(context)
@@ skipping 247 matching lines @@
      * @return {!Element}
      */
     statusBarItem: function()
     {
         if (this._initialized)
             return this._toggleScreencastButton.element;
         this._statusBarPlaceholder = document.createElement("div");
         return this._statusBarPlaceholder;
     }
 };