Use DEFINE_NODE_TYPE_CASTS instead of using manual toSVGFooElement()

Source/core/svg/SVGFEMergeNodeElement.h

Index: Source/core/svg/SVGFEMergeNodeElement.h
diff --git a/Source/core/svg/SVGFEMergeNodeElement.h b/Source/core/svg/SVGFEMergeNodeElement.h
index 9bfe59aec6ee297a1f3105ec527116b6db542732..b93938a225137680f37fcd5c6ae434954828f505 100644
--- a/Source/core/svg/SVGFEMergeNodeElement.h
+++ b/Source/core/svg/SVGFEMergeNodeElement.h
@@ -45,11 +45,7 @@ private:
     END_DECLARE_ANIMATED_PROPERTIES
 };
 
-inline SVGFEMergeNodeElement* toSVGFEMergeNodeElement(Node* node)
-{
-    ASSERT_WITH_SECURITY_IMPLICATION(!node || node->hasTagName(SVGNames::feMergeNodeTag));
-    return static_cast<SVGFEMergeNodeElement*>(node);
-}
+DEFINE_NODE_TYPE_CASTS(SVGFEMergeNodeElement, hasTagName(SVGNames::feMergeNodeTag));
 
 } // namespace WebCore