Introduce DEFINE_DOCUMENT_TYPE_CASTS, and use it

Source/core/svg/SVGDocument.h

 /*
  * Copyright (C) 2004, 2005 Nikolas Zimmermann <zimmermann@kde.org>
  * Copyright (C) 2004, 2005, 2006, 2007 Rob Buis <buis@kde.org>
  *
  * 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.
  *
  * This library is distributed in the hope that it will be useful,
@@ skipping 37 matching lines @@
     virtual PassRefPtr<Document> cloneDocumentWithoutChildren() OVERRIDE FINAL;
 
 private:
     explicit SVGDocument(const DocumentInit&);
 
     virtual bool childShouldCreateRenderer(const Node& child) const;
 
     FloatPoint m_translate;
 };
 
-inline SVGDocument* toSVGDocument(Document* document)
-{
-    ASSERT_WITH_SECURITY_IMPLICATION(!document || document->isSVGDocument());
-    return static_cast<SVGDocument*>(document);
-}
-
-inline const SVGDocument* toSVGDocument(const Document* document)
-{
-    ASSERT_WITH_SECURITY_IMPLICATION(!document || document->isSVGDocument());
-    return static_cast<const SVGDocument*>(document);
-}
-
-// This will catch anyone doing an unnecessary cast.
-void toSVGDocument(const SVGDocument*);
+DEFINE_DOCUMENT_TYPE_CASTS(SVGDocument);
 
 } // namespace WebCore
 
 #endif // SVGDocument_h