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

Source/core/html/HTMLOptGroupElement.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) 2004, 2005, 2006, 2007, 2008, 2010 Apple Inc. All rights reserved.
  *           (C) 2006 Alexey Proskuryakov (ap@nypop.com)
  *
  * 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
@@ skipping 58 matching lines @@
     HTMLElement::parseAttribute(name, value);
     recalcSelectOptions();
 
     if (name == disabledAttr)
         didAffectSelector(AffectedSelectorDisabled | AffectedSelectorEnabled);
 }
 
 void HTMLOptGroupElement::recalcSelectOptions()
 {
     ContainerNode* select = parentNode();
-    while (select && !select->hasTagName(selectTag))
+    while (select && !isHTMLSelectElement(*select))
         select = select->parentNode();
     if (select)
         toHTMLSelectElement(select)->setRecalcListItems();
 }
 
 void HTMLOptGroupElement::attach(const AttachContext& context)
 {
     if (context.resolvedStyle) {
         ASSERT(!m_style || m_style == context.resolvedStyle);
         m_style = context.resolvedStyle;
@@ skipping 31 matching lines @@
     itemText = itemText.stripWhiteSpace();
     // We want to collapse our whitespace too.  This will match other browsers.
     itemText = itemText.simplifyWhiteSpace();
 
     return itemText;
 }
 
 HTMLSelectElement* HTMLOptGroupElement::ownerSelectElement() const
 {
     ContainerNode* select = parentNode();
-    while (select && !select->hasTagName(selectTag))
+    while (select && !isHTMLSelectElement(*select))
         select = select->parentNode();
 
     if (!select)
        return 0;
 
     return toHTMLSelectElement(select);
 }
 
 void HTMLOptGroupElement::accessKeyAction(bool)
 {
     HTMLSelectElement* select = ownerSelectElement();
     // send to the parent to bring focus to the list box
     if (select && !select->focused())
         select->accessKeyAction(false);
 }
 
 } // namespace