Move RenderSVGResource::cast() to RenderSVGResourceContainer

Source/core/rendering/svg/RenderSVGResourceContainer.h

Index: Source/core/rendering/svg/RenderSVGResourceContainer.h
diff --git a/Source/core/rendering/svg/RenderSVGResourceContainer.h b/Source/core/rendering/svg/RenderSVGResourceContainer.h
index e7a8a5f0f702c4f3d32116a62673114c46a009fb..4d958f6ceb8562ce370c4e9150b1c3c9847f671a 100644
--- a/Source/core/rendering/svg/RenderSVGResourceContainer.h
+++ b/Source/core/rendering/svg/RenderSVGResourceContainer.h
@@ -39,6 +39,15 @@ public:
 
     virtual bool isSVGResourceContainer() const OVERRIDE FINAL { return true; }
 
+    template<class Renderer>
+    Renderer* cast()
+    {
+        if (Renderer::s_resourceType == resourceType())
+            return static_cast<Renderer*>(this);
+
+        return 0;
+    }
+
     static AffineTransform transformOnNonScalingStroke(RenderObject*, const AffineTransform& resourceTransform);
 
     void idChanged();