Devirtualize Document class type checking

Source/core/html/HTMLDocument.h

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 1999 Antti Koivisto (koivisto@kde.org)
  * Copyright (C) 2004, 2006, 2007, 2008, 2009 Apple Inc. All rights reserved.
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Library General Public
  * License as published by the Free Software Foundation; either
  * version 2 of the License, or (at your option) any later version.
  *
@@ skipping 59 matching lines @@
     void removeNamedItem(const AtomicString& name);
     bool hasNamedItem(AtomicStringImpl* name);
 
     void addExtraNamedItem(const AtomicString& name);
     void removeExtraNamedItem(const AtomicString& name);
     bool hasExtraNamedItem(AtomicStringImpl* name);
 
     static bool isCaseSensitiveAttribute(const QualifiedName&);
 
 protected:
-    HTMLDocument(Frame*, const KURL&);
+    HTMLDocument(Frame*, const KURL&, unsigned extendedDocumentClass = DefaultDocumentClass);
 
 private:
     virtual PassRefPtr<Element> createElement(const AtomicString& tagName, ExceptionCode&);
 
     virtual bool isFrameSet() const;
     virtual PassRefPtr<DocumentParser> createParser();
 
     void addItemToMap(HashCountedSet<AtomicStringImpl*>&, const AtomicString&);
     void removeItemFromMap(HashCountedSet<AtomicStringImpl*>&, const AtomicString&);
 
@@ skipping 24 matching lines @@
     ASSERT_WITH_SECURITY_IMPLICATION(!document || document->isHTMLDocument());
     return static_cast<const HTMLDocument*>(document);
 }
 
 // This will catch anyone doing an unnecessary cast.
 void toHTMLDocument(const HTMLDocument*);
 
 } // namespace WebCore
 
 #endif // HTMLDocument_h