Introduce isSVGFontElement() and isSVGImageElement(), and use them

Source/core/svg/SVGFontElement.h

 /*
  * Copyright (C) 2007 Eric Seidel <eric@webkit.org>
  * Copyright (C) 2007 Nikolas Zimmermann <zimmermann@kde.org>
  * Copyright (C) Research In Motion Limited 2010. All rights reserved.
  *
  * 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.
  *
@@ skipping 71 matching lines @@
         DECLARE_ANIMATED_BOOLEAN(ExternalResourcesRequired, externalResourcesRequired)
     END_DECLARE_ANIMATED_PROPERTIES
 
     KerningPairVector m_horizontalKerningPairs;
     KerningPairVector m_verticalKerningPairs;
     SVGGlyphMap m_glyphMap;
     Glyph m_missingGlyph;
     bool m_isGlyphCacheValid;
 };
 
+inline bool isSVGFontElement(const Node* node)
+{
+    return node->hasTagName(SVGNames::fontTag);
+}
+
 inline SVGFontElement* toSVGFontElement(Node* node)
 {
-    ASSERT_WITH_SECURITY_IMPLICATION(!node || node->hasTagName(SVGNames::fontTag));
+    ASSERT_WITH_SECURITY_IMPLICATION(!node || isSVGFontElement(node));
     return static_cast<SVGFontElement*>(node);
 }
 
 } // namespace WebCore
 
 #endif // ENABLE(SVG_FONTS)
 #endif