Use new is*Element() helper functions in DOM code

Source/core/dom/StyleElement.cpp

 /*
  * Copyright (C) 2006, 2007 Rob Buis
  * Copyright (C) 2008 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.
  *
  * This library is distributed in the hope that it will be useful,
@@ skipping 67 matching lines @@
 
     document.removedStyleSheet(removedSheet.get(), RecalcStyleDeferred, AnalyzedStyleUpdate);
 }
 
 void StyleElement::clearDocumentData(Document& document, Element* element)
 {
     if (m_sheet)
         m_sheet->clearOwnerNode();
 
     if (element->inDocument())
-        document.styleEngine()->removeStyleSheetCandidateNode(element, element->hasTagName(HTMLNames::styleTag) ? toHTMLStyleElement(element)->scopingNode() :  0);
+        document.styleEngine()->removeStyleSheetCandidateNode(element, isHTMLStyleElement(*element) ? toHTMLStyleElement(*element).scopingNode() :  0);
 }
 
 void StyleElement::childrenChanged(Element* element)
 {
     ASSERT(element);
     if (m_createdByParser)
         return;
 
     process(element);
 }
@@ skipping 66 matching lines @@
     document.styleEngine()->removePendingSheet(m_sheet->ownerNode());
     return true;
 }
 
 void StyleElement::startLoadingDynamicSheet(Document& document)
 {
     document.styleEngine()->addPendingSheet();
 }
 
 }