Add initial support for [Exposed=xx] extended IDL attribute

Source/core/dom/URL.idl

 /*
  * Copyright (C) 2011 Google Inc. All rights reserved.
  * Copyright (C) 2012 Motorola Mobility Inc.
  *
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  * modification, are permitted provided that the following conditions
  * are met:
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  *     notice, this list of conditions and the following disclaimer.
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 [
-    GlobalContext=Window&WorkerGlobalScope,
+    Exposed=Window&Worker,
     RaisesException=Constructor,
     Constructor(DOMString url),
     Constructor(DOMString url, URL base),
     Constructor(DOMString url, DOMString base),
     ImplementedAs=DOMURL,
     WillBeGarbageCollected
 ] interface URL {
     [RaisesException, CallWith=ExecutionContext,TreatReturnedNullStringAs=Null] static DOMString createObjectURL(Blob? blob);
     [CallWith=ExecutionContext] static void revokeObjectURL(DOMString url);
 };
 
 URL implements URLUtils;