Make more [TreatNullAs=NullString] DOMString arguments nullable

Source/core/frame/Window.idl

 /*
  * Copyright (C) 2006, 2007, 2008, 2009 Apple Inc. All rights reserved.
  * Copyright (C) 2011 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.
  * 2. Redistributions in binary form must reproduce the above copyright
@@ skipping 122 matching lines @@
     readonly attribute Document document;
 
     // CSSOM View Module
     MediaQueryList matchMedia(DOMString query);
 
     // styleMedia has been removed from the CSSOM View specification.
     readonly attribute StyleMedia styleMedia;
 
     // DOM Level 2 Style Interface
     CSSStyleDeclaration getComputedStyle([Default=Undefined] optional Element element,
-                                                            [TreatNullAs=NullString, TreatUndefinedAs=NullString, Default=Undefined] optional DOMString pseudoElement);
+                                         [TreatUndefinedAs=NullString, Default=Undefined] optional DOMString? pseudoElement);
 
     // WebKit extensions
     [MeasureAs=GetMatchedCSSRules] CSSRuleList getMatchedCSSRules([Default=Undefined] optional Element element,
-                                                                  [TreatNullAs=NullString, TreatUndefinedAs=NullString, Default=Undefined] optional DOMString pseudoElement);
+                                                                  [TreatUndefinedAs=NullString, Default=Undefined] optional DOMString? pseudoElement);
 
     [Replaceable] readonly attribute double devicePixelRatio;
 
     [MeasureAs=PrefixedConvertPointFromPageToNode] WebKitPoint webkitConvertPointFromPageToNode([Default=Undefined] optional Node node,
                                                                                                 [Default=Undefined] optional WebKitPoint p);
     [MeasureAs=PrefixedConvertPointFromNodeToPage] WebKitPoint webkitConvertPointFromNodeToPage([Default=Undefined] optional Node node,
                                                                                                 [Default=Undefined] optional WebKitPoint p);
 
     [RuntimeEnabled=ApplicationCache, LogActivity=GetterOnly] readonly attribute ApplicationCache applicationCache;
 
@@ skipping 50 matching lines @@
     [DoNotCheckSignature, DoNotCheckSecurity, Custom, NotEnumerable] stringifier;
 
     [NotEnumerable] getter Window (unsigned long index);
     [Custom, NotEnumerable] getter Window (DOMString name);
 };
 
 Window implements GlobalEventHandlers;
 Window implements WindowBase64;
 Window implements WindowEventHandlers;
 Window implements WindowTimers;