Replace elementHasLegalLinkAttribute() helper with virtual function

Source/core/dom/Element.h

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 1999 Antti Koivisto (koivisto@kde.org)
  *           (C) 2001 Peter Kelly (pmk@post.com)
  *           (C) 2001 Dirk Mueller (mueller@kde.org)
  * Copyright (C) 2003, 2004, 2005, 2006, 2007, 2008, 2009, 2010, 2011, 2013 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
@@ skipping 260 matching lines @@
 
     enum AttributeModificationReason {
         ModifiedDirectly,
         ModifiedByCloning
     };
 
     // This method is called whenever an attribute is added, changed or removed.
     virtual void attributeChanged(const QualifiedName&, const AtomicString&, AttributeModificationReason = ModifiedDirectly);
     virtual void parseAttribute(const QualifiedName&, const AtomicString&) { }
 
+    virtual bool hasLegalLinkAttribute(const QualifiedName&) const;
+
     // Only called by the parser immediately after element construction.
     void parserSetAttributes(const Vector<Attribute>&);
 
     // Remove attributes that might introduce scripting from the vector leaving the element unchanged.
     void stripScriptingAttributes(Vector<Attribute>&) const;
 
     const ElementData* elementData() const { return m_elementData.get(); }
     UniqueElementData& ensureUniqueElementData();
 
     void synchronizeAllAttributes() const;
@@ skipping 601 matching lines @@
     template <> inline bool isElementOfType<const thisType>(const Element& element) { return element.predicate; } \
     DEFINE_NODE_TYPE_CASTS(thisType, predicate)
 
 #define DEFINE_ELEMENT_TYPE_CASTS_WITH_FUNCTION(thisType) \
     template <> inline bool isElementOfType<const thisType>(const Element& element) { return is##thisType(element); } \
     DEFINE_NODE_TYPE_CASTS_WITH_FUNCTION(thisType)
 
 } // namespace
 
 #endif