Use DEFINE_NODE_TYPE_CASTS instead of using manual toHTMLFooElement()

Source/core/html/HTMLStyleElement.h

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 1999 Antti Koivisto (koivisto@kde.org)
  * Copyright (C) 2003, 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 91 matching lines @@
     };
     ScopedStyleRegistrationState m_scopedStyleRegistrationState;
 };
 
 inline bool isHTMLStyleElement(Node* node)
 {
     ASSERT(node);
     return node->hasTagName(HTMLNames::styleTag);
 }
 
-inline HTMLStyleElement* toHTMLStyleElement(Node* node)
-{
-    ASSERT_WITH_SECURITY_IMPLICATION(!node || node->hasTagName(HTMLNames::styleTag));
-    return static_cast<HTMLStyleElement*>(node);
-}
+DEFINE_NODE_TYPE_CASTS(HTMLStyleElement, hasTagName(HTMLNames::styleTag));
 
 } //namespace
 
 #endif