Introduce DEFINE_RENDER_SVG_RESOURCE_TYPE_CASTS, and use it

Source/core/rendering/svg/RenderSVGResourceMasker.h

 /*
  * Copyright (C) Research In Motion Limited 2009-2010. 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.
  *
  * This library is distributed in the hope that it will be useful,
  * but WITHOUT ANY WARRANTY; without even the implied warranty of
@@ skipping 45 matching lines @@
 
 private:
     void calculateMaskContentRepaintRect();
     void drawMaskForRenderer(GraphicsContext*, const FloatRect& targetBoundingBox);
     PassRefPtr<DisplayList> asDisplayList(GraphicsContext*, const AffineTransform&);
 
     RefPtr<DisplayList> m_maskContentDisplayList;
     FloatRect m_maskContentBoundaries;
 };
 
-inline RenderSVGResourceMasker* toRenderSVGResourceMasker(RenderSVGResource* resource)
-{
-    ASSERT_WITH_SECURITY_IMPLICATION(!resource || resource->resourceType() == MaskerResourceType);
-    return static_cast<RenderSVGResourceMasker*>(resource);
-}
+DEFINE_RENDER_SVG_RESOURCE_TYPE_CASTS(RenderSVGResourceMasker, MaskerResourceType);
 
 }
 
 #endif