Use new is*Element() helper functions more in editing code

Source/core/editing/MarkupAccumulator.cpp

 /*
  * Copyright (C) 2004, 2005, 2006, 2007, 2008, 2009, 2012 Apple Inc. All rights reserved.
  * Copyright (C) 2009, 2010 Google Inc. All rights reserved.
  *
  * 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 121 matching lines @@
     }
 
     Namespaces namespaceHash;
     if (namespaces)
         namespaceHash = *namespaces;
 
     if (!childrenOnly)
         appendStartTag(targetNode, &namespaceHash);
 
     if (!(serializeAsHTMLDocument(targetNode) && elementCannotHaveEndTag(targetNode))) {
-        Node* current = targetNode.hasTagName(templateTag) ? toHTMLTemplateElement(targetNode).content()->firstChild() : targetNode.firstChild();
+        Node* current = isHTMLTemplateElement(targetNode) ? toHTMLTemplateElement(targetNode).content()->firstChild() : targetNode.firstChild();
         for ( ; current; current = current->nextSibling())
             serializeNodesWithNamespaces(*current, IncludeNode, &namespaceHash, tagNamesToSkip);
     }
 
     if (!childrenOnly)
         appendEndTag(targetNode);
 }
 
 String MarkupAccumulator::resolveURLIfNeeded(const Element& element, const String& urlString) const
 {
@@ skipping 397 matching lines @@
 }
 
 bool MarkupAccumulator::serializeAsHTMLDocument(const Node& node) const
 {
     if (m_serializationType == ForcedXML)
         return false;
     return node.document().isHTMLDocument();
 }
 
 }