Introduce DEFINE_RENDER_SVG_RESOURCE_TYPE_CASTS, and use it

Source/core/rendering/svg/RenderSVGResourceRadialGradient.h

Index: Source/core/rendering/svg/RenderSVGResourceRadialGradient.h
diff --git a/Source/core/rendering/svg/RenderSVGResourceRadialGradient.h b/Source/core/rendering/svg/RenderSVGResourceRadialGradient.h
index 3705c818d5bd0d4f9f14bb1f3f9e8f5931aece0e..43ee07601e08ef21497554a3dea75913c98415ae 100644
--- a/Source/core/rendering/svg/RenderSVGResourceRadialGradient.h
+++ b/Source/core/rendering/svg/RenderSVGResourceRadialGradient.h
@@ -52,11 +52,7 @@ private:
     RadialGradientAttributes m_attributes;
 };
 
-inline RenderSVGResourceRadialGradient* toRenderSVGResourceRadialGradient(RenderSVGResourceContainer* resource)
-{
-    ASSERT_WITH_SECURITY_IMPLICATION(!resource || resource->resourceType() == RadialGradientResourceType);
-    return static_cast<RenderSVGResourceRadialGradient*>(resource);
-}
+DEFINE_RENDER_SVG_RESOURCE_TYPE_CASTS(RenderSVGResourceRadialGradient, RadialGradientResourceType);
 
 }