Add toRenderSVGResourceClipper() fuction, and use it.

Source/core/rendering/svg/RenderSVGResourceClipper.h

Index: Source/core/rendering/svg/RenderSVGResourceClipper.h
diff --git a/Source/core/rendering/svg/RenderSVGResourceClipper.h b/Source/core/rendering/svg/RenderSVGResourceClipper.h
index 7344e7eff60f9643a574e1de3a28fdd844878fe4..09c481331485f1018442864f29ba931d42d0be1f 100644
--- a/Source/core/rendering/svg/RenderSVGResourceClipper.h
+++ b/Source/core/rendering/svg/RenderSVGResourceClipper.h
@@ -20,6 +20,7 @@
 #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"
 
@@ -73,6 +74,12 @@ private:
     bool m_inClipExpansion;
 };
 
+inline RenderSVGResourceClipper* toRenderSVGResourceClipper(RenderSVGResource* resource)
+{
+    ASSERT_WITH_SECURITY_IMPLICATION(!resource || resource->resourceType() == ClipperResourceType);
+    return static_cast<RenderSVGResourceClipper*>(resource);
+}
+
 }
 
 #endif