Replace elementHasLegalLinkAttribute() helper with virtual function

Source/core/html/HTMLFormElement.cpp

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 1999 Antti Koivisto (koivisto@kde.org)
  *           (C) 2001 Dirk Mueller (mueller@kde.org)
  * Copyright (C) 2004, 2005, 2006, 2007, 2008, 2009 Apple Inc. All rights reserved.
  *           (C) 2006 Alexey Proskuryakov (ap@nypop.com)
  *
  * 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
@@ skipping 494 matching lines @@
     m_associatedElementsAreDirty = true;
     m_associatedElements.clear();
     removeFromPastNamesMap(toHTMLElement(e));
 }
 
 bool HTMLFormElement::isURLAttribute(const Attribute& attribute) const
 {
     return attribute.name() == actionAttr || HTMLElement::isURLAttribute(attribute);
 }
 
+bool HTMLFormElement::hasLegalLinkAttribute(const QualifiedName& name) const
+{
+    return name == actionAttr || HTMLElement::hasLegalLinkAttribute(name);
+}
+
 void HTMLFormElement::associate(HTMLImageElement& e)
 {
     m_imageElementsAreDirty = true;
     m_imageElements.clear();
 }
 
 void HTMLFormElement::disassociate(HTMLImageElement& e)
 {
     m_imageElementsAreDirty = true;
     m_imageElements.clear();
@@ skipping 258 matching lines @@
 }
 
 void HTMLFormElement::setDemoted(bool demoted)
 {
     if (demoted)
         UseCounter::count(document(), UseCounter::DemotedFormElement);
     m_wasDemoted = demoted;
 }
 
 } // namespace