Add toRenderSVGResourceFilter() fuction, and use it.

Source/core/rendering/svg/RenderSVGResourceFilter.h

Index: Source/core/rendering/svg/RenderSVGResourceFilter.h
diff --git a/Source/core/rendering/svg/RenderSVGResourceFilter.h b/Source/core/rendering/svg/RenderSVGResourceFilter.h
index 36b91ae9e92e89ed27c1a3615a560214a307f873..ebb4c9f3689a5d7b7ee49f3d97c2fd47ae1eabe9 100644
--- a/Source/core/rendering/svg/RenderSVGResourceFilter.h
+++ b/Source/core/rendering/svg/RenderSVGResourceFilter.h
@@ -88,10 +88,10 @@ private:
     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);
 }
 
 }