Use DEFINE_NODE_TYPE_CASTS instead of using manual toSVGFooElement()

Source/core/svg/SVGMPathElement.h

 /*
  * Copyright (C) 2007 Eric Seidel <eric@webkit.org>
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Library General Public
  * License as published by the Free Software Foundation; either
  * version 2 of the License, or (at your option) any later version.
  *
  * This library is distributed in the hope that it will be useful,
  * but WITHOUT ANY WARRANTY; without even the implied warranty of
@@ skipping 46 matching lines @@
 
     virtual bool rendererIsNeeded(const RenderStyle&) OVERRIDE { return false; }
     void notifyParentOfPathChange(ContainerNode*);
 
     BEGIN_DECLARE_ANIMATED_PROPERTIES(SVGMPathElement)
         DECLARE_ANIMATED_STRING(Href, href)
         DECLARE_ANIMATED_BOOLEAN(ExternalResourcesRequired, externalResourcesRequired)
     END_DECLARE_ANIMATED_PROPERTIES
 };
 
-inline SVGMPathElement* toSVGMPathElement(Node* node)
-{
-    ASSERT_WITH_SECURITY_IMPLICATION(!node || node->hasTagName(SVGNames::mpathTag));
-    return static_cast<SVGMPathElement*>(node);
-}
+DEFINE_NODE_TYPE_CASTS(SVGMPathElement, hasTagName(SVGNames::mpathTag));
 
 } // namespace WebCore
 
 #endif // SVGMPathElement_h