Use DEFINE_NODE_TYPE_CASTS instead of using manual toSVGFooElement()

Source/core/svg/SVGTextElement.h

 /*
  * Copyright (C) 2004, 2005, 2008 Nikolas Zimmermann <zimmermann@kde.org>
  * Copyright (C) 2004, 2005, 2006, 2008 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 23 matching lines @@
 
 private:
     SVGTextElement(const QualifiedName&, Document&);
 
     virtual bool supportsFocus() const OVERRIDE { return hasFocusEventListeners(); }
 
     virtual RenderObject* createRenderer(RenderStyle*);
     virtual bool childShouldCreateRenderer(const Node& child) const;
 };
 
-inline SVGTextElement* toSVGTextElement(Node* node)
-{
-    ASSERT_WITH_SECURITY_IMPLICATION(!node || node->hasTagName(SVGNames::textTag));
-    return static_cast<SVGTextElement*>(node);
-}
+DEFINE_NODE_TYPE_CASTS(SVGTextElement, hasTagName(SVGNames::textTag));
 
 } // namespace WebCore
 
 #endif