DevTools: Code fixes for the Closure compiler roll

Source/devtools/front_end/sources/StyleSheetOutlineDialog.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 31 matching lines @@
 }
 
 /**
  * @param {!WebInspector.View} view
  * @param {!WebInspector.UISourceCode} uiSourceCode
  * @param {function(number, number)} selectItemCallback
  */
 WebInspector.StyleSheetOutlineDialog.show = function(view, uiSourceCode, selectItemCallback)
 {
     if (WebInspector.Dialog.currentInstance())
-        return null;
+        return;
     var delegate = new WebInspector.StyleSheetOutlineDialog(uiSourceCode, selectItemCallback);
     var filteredItemSelectionDialog = new WebInspector.FilteredItemSelectionDialog(delegate);
     WebInspector.Dialog.show(view.element, filteredItemSelectionDialog);
 }
 
 WebInspector.StyleSheetOutlineDialog.prototype = {
     /**
      * @return {number}
      */
     itemCount: function()
@@ skipping 48 matching lines @@
             this._selectItemCallback(lineNumber, rule.columnNumber);
     },
 
     dispose: function()
     {
         this._cssParser.dispose();
     },
 
     __proto__: WebInspector.SelectionDialogContentProvider.prototype
 }