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

Source/core/html/HTMLMetaElement-in.cpp

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 1999 Antti Koivisto (koivisto@kde.org)
  *           (C) 2001 Dirk Mueller (mueller@kde.org)
  * Copyright (C) 2003, 2010 Apple Inc. 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 431 matching lines @@
         process();
     return InsertionDone;
 }
 
 static bool inDocumentHead(HTMLMetaElement* element)
 {
     if (!element->inDocument())
         return false;
 
     for (Element* current = element; current; current = current->parentElement()) {
-        if (current->hasTagName(HTMLNames::headTag))
+        if (isHTMLHeadElement(*current))
             return true;
     }
     return false;
 }
 
 void HTMLMetaElement::process()
 {
     if (!inDocument())
         return;
 
@@ skipping 32 matching lines @@
 {
     return getAttribute(http_equivAttr);
 }
 
 const AtomicString& HTMLMetaElement::name() const
 {
     return getNameAttribute();
 }
 
 }