Add toRenderSVGResourceFilter() fuction, and use it.

Source/core/rendering/svg/RenderSVGResourceFilter.h

 /*
  * Copyright (C) 2004, 2005, 2006, 2007 Nikolas Zimmermann <zimmermann@kde.org>
  * Copyright (C) 2004, 2005 Rob Buis <buis@kde.org>
  * Copyright (C) 2005 Eric Seidel <eric@webkit.org>
  * Copyright (C) 2009 Dirk Schulze <krit@webkit.org>
  * Copyright (C) Research In Motion Limited 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
@@ skipping 70 matching lines @@
     virtual RenderSVGResourceType resourceType() const { return s_resourceType; }
     static RenderSVGResourceType s_resourceType;
 
     FloatRect drawingRegion(RenderObject*) const;
 private:
     bool fitsInMaximumImageSize(const FloatSize&, FloatSize&);
 
     HashMap<RenderObject*, FilterData*> m_filter;
 };
 
-inline RenderSVGResourceFilter* toRenderSVGFilter(RenderObject* object)
+inline RenderSVGResourceFilter* toRenderSVGResourceFilter(RenderSVGResource* resource)

[tkent, 2013/09/12 03:30:46]

We should have both of toRenderSVGResourceFilter(RenderObject*) and
toRenderSVGResourceFilter(RenderSVGResource*).

 {
-    ASSERT_WITH_SECURITY_IMPLICATION(!object || object->isSVGResourceFilter());
-    return static_cast<RenderSVGResourceFilter*>(object);
+    ASSERT_WITH_SECURITY_IMPLICATION(!resource || resource->resourceType() == FilterResourceType);
+    return static_cast<RenderSVGResourceFilter*>(resource);
 }
 
 }
 
 #endif