Devirtualize Document class type checking

Source/core/html/HTMLDocument.cpp

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 1999 Antti Koivisto (koivisto@kde.org)
  * Copyright (C) 2003, 2004, 2005, 2006, 2007, 2008 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 63 matching lines @@
 #include "core/page/Page.h"
 #include "core/page/Settings.h"
 #include "core/platform/HashTools.h"
 #include "core/platform/KURL.h"
 #include <wtf/text/CString.h>
 
 namespace WebCore {
 
 using namespace HTMLNames;
 
-HTMLDocument::HTMLDocument(Frame* frame, const KURL& url)
-    : Document(frame, url, false, true)
+HTMLDocument::HTMLDocument(Frame* frame, const KURL& url, unsigned extendedDocumentClass)
+    : Document(frame, url, HTMLDocumentClass | extendedDocumentClass)
 {
     ScriptWrappable::init(this);
     clearXMLVersion();
 }
 
 HTMLDocument::~HTMLDocument()
 {
 }
 
 int HTMLDocument::width()
@@ skipping 304 matching lines @@
     // But I do see it in the documentation for Mozilla.
 }
 
 bool HTMLDocument::isFrameSet() const
 {
     HTMLElement* bodyElement = body();
     return bodyElement && bodyElement->hasTagName(framesetTag);
 }
 
 }