Add toRenderSVGResourceClipper() fuction, and use it.

Source/core/rendering/svg/RenderSVGResourceClipper.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
  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  * Library General Public License for more details.
  *
  * You should have received a copy of the GNU Library General Public License
  * along with this library; see the file COPYING.LIB.  If not, write to
  * the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
  * Boston, MA 02110-1301, USA.
  */
 
 #ifndef RenderSVGResourceClipper_h
 #define RenderSVGResourceClipper_h
 
+#include "core/rendering/svg/RenderSVGResource.h"

[tkent, 2013/09/11 21:37:51]

I think we don't need to include it.

 #include "core/rendering/svg/RenderSVGResourceContainer.h"
 #include "core/svg/SVGClipPathElement.h"
 
 namespace WebCore {
 
 struct ClipperData {
     WTF_MAKE_FAST_ALLOCATED;
 public:
     enum ClipMode { PathOnlyClipMode, MaskClipMode };
 
@@ skipping 33 matching lines @@
     void drawMaskContent(GraphicsContext*, const FloatRect& targetBoundingBox);
     void calculateClipContentRepaintRect();
 
     FloatRect m_clipBoundaries;
     HashMap<const RenderObject*, OwnPtr<ClipperData> > m_rendererToClipperMap;
 
     // Reference cycle detection.
     bool m_inClipExpansion;
 };
 
+inline RenderSVGResourceClipper* toRenderSVGResourceClipper(RenderSVGResource* resource)
+{
+    ASSERT_WITH_SECURITY_IMPLICATION(!resource || resource->resourceType() == ClipperResourceType);
+    return static_cast<RenderSVGResourceClipper*>(resource);
+}
+
 }
 
 #endif