Apply DEFINE_NODE_TYPE_CASTS_WITH_FUNCTION to HTMLUnknownElement

Source/core/html/HTMLUnknownElement.h

 /*
  * Copyright (c) 2011 Code Aurora Forum. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *     * Redistributions of source code must retain the above copyright
  *       notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
  *       copyright notice, this list of conditions and the following
@@ skipping 33 matching lines @@
     virtual bool isHTMLUnknownElement() const OVERRIDE { return true; }
 
 private:
     HTMLUnknownElement(const QualifiedName& tagName, Document& document)
         : HTMLElement(tagName, document)
     {
         ScriptWrappable::init(this);
     }
 };
 
-inline HTMLUnknownElement* toHTMLUnknownElement(HTMLElement* element)
+inline bool isHTMLUnknownElement(const Node& node)
 {
-    ASSERT_WITH_SECURITY_IMPLICATION(!element || element->isHTMLUnknownElement());
-    return static_cast<HTMLUnknownElement*>(element);
+    return node.isElementNode() && toHTMLElement(node).isHTMLUnknownElement();
 }
 
+DEFINE_NODE_TYPE_CASTS_WITH_FUNCTION(HTMLUnknownElement);
+
 } // namespace
 
 #endif