Use DEFINE_NODE_TYPE_CASTS instead of using manual toSVGFooElement()

Source/core/svg/SVGFEMergeNodeElement.h

 /*
  * Copyright (C) 2004, 2005 Nikolas Zimmermann <zimmermann@kde.org>
  * Copyright (C) 2004, 2005, 2006 Rob Buis <buis@kde.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,
@@ skipping 27 matching lines @@
     virtual void parseAttribute(const QualifiedName&, const AtomicString&) OVERRIDE;
     virtual void svgAttributeChanged(const QualifiedName&);
 
     virtual bool rendererIsNeeded(const RenderStyle&) OVERRIDE { return false; }
 
     BEGIN_DECLARE_ANIMATED_PROPERTIES(SVGFEMergeNodeElement)
         DECLARE_ANIMATED_STRING(In1, in1)
     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
 
 #endif