Use DEFINE_NODE_TYPE_CASTS instead of using manual toHTMLFooElement()

Source/core/html/HTMLFormElement.h

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 1999 Antti Koivisto (koivisto@kde.org)
  *           (C) 2000 Dirk Mueller (mueller@kde.org)
  * Copyright (C) 2004, 2005, 2006, 2007, 2008, 2009, 2010 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 169 matching lines @@
     bool m_isInResetFunction;
 
     bool m_wasDemoted;
 
     void requestAutocompleteTimerFired(Timer<HTMLFormElement>*);
 
     Vector<RefPtr<Event> > m_pendingAutocompleteEvents;
     Timer<HTMLFormElement> m_requestAutocompleteTimer;
 };
 
-inline HTMLFormElement* toHTMLFormElement(Node* node)
-{
-    ASSERT_WITH_SECURITY_IMPLICATION(!node || node->hasTagName(HTMLNames::formTag));
-    return static_cast<HTMLFormElement*>(node);
-}
+DEFINE_NODE_TYPE_CASTS(HTMLFormElement, hasTagName(HTMLNames::formTag));
 
 } // namespace WebCore
 
 #endif // HTMLFormElement_h