Turn DocumentParser::pinToMainThread into a cleaner api

Source/core/html/TextDocument.cpp

 /*
  * Copyright (C) 2006, 2007, 2008 Apple 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
  *    notice, this list of conditions and the following disclaimer in the
@@ skipping 20 matching lines @@
 
 TextDocument::TextDocument(const DocumentInit& initializer)
     : HTMLDocument(initializer)
 {
     setCompatibilityMode(QuirksMode);
     lockCompatibilityMode();
 }
 
 PassRefPtrWillBeRawPtr<DocumentParser> TextDocument::createParser()
 {
-    return TextDocumentParser::create(*this);
+    return TextDocumentParser::create(*this, parserSynchronizationPolicy());
 }
 
 }