Use DEFINE_NODE_TYPE_CASTS instead of using manual toSVGFooElement()

Source/core/svg/SVGMissingGlyphElement.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 18 matching lines @@
 class SVGMissingGlyphElement FINAL : public SVGElement {
 public:
     static PassRefPtr<SVGMissingGlyphElement> create(const QualifiedName&, Document&);
 
 private:
     SVGMissingGlyphElement(const QualifiedName&, Document&);
 
     virtual bool rendererIsNeeded(const RenderStyle&) { return false; }
 };
 
-inline SVGMissingGlyphElement* toSVGMissingGlyphElement(Node* node)
-{
-    ASSERT_WITH_SECURITY_IMPLICATION(!node || node->hasTagName(SVGNames::missing_glyphTag));
-    return static_cast<SVGMissingGlyphElement*>(node);
-}
+DEFINE_NODE_TYPE_CASTS(SVGMissingGlyphElement, hasTagName(SVGNames::missing_glyphTag));
 
 } // namespace WebCore
 
 #endif // ENABLE(SVG_FONTS)
 #endif