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

Source/core/loader/cache/CachedFont.cpp

 /*
  * Copyright (C) 2006, 2007, 2008 Apple Inc. All rights reserved.
  * Copyright (C) 2009 Torch Mobile, Inc.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
@@ skipping 112 matching lines @@
     if (!list)
         return 0;
 
     unsigned listLength = list->length();
     if (!listLength)
         return 0;
 
 #ifndef NDEBUG
     for (unsigned i = 0; i < listLength; ++i) {
         ASSERT(list->item(i));
-        ASSERT(list->item(i)->hasTagName(SVGNames::fontTag));
+        ASSERT(isSVGFontElement(list->item(i)));
     }
 #endif
 
     if (fontName.isEmpty())
         return toSVGFontElement(list->item(0));
 
     for (unsigned i = 0; i < listLength; ++i) {
         SVGFontElement* element = toSVGFontElement(list->item(i));
         if (element->getIdAttribute() == fontName)
             return element;
@@ skipping 23 matching lines @@
 {
     MemoryClassInfo info(memoryObjectInfo, this, WebCoreMemoryTypes::CachedResourceFont);
     CachedResource::reportMemoryUsage(memoryObjectInfo);
 #if ENABLE(SVG_FONTS)
     info.addMember(m_externalSVGDocument, "externalSVGDocument");
 #endif
     info.addMember(m_fontData, "fontData");
 }
 
 }