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

Source/core/html/HTMLInputElement.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, 2009, 2010, 2011 Apple Inc. All rights reserved.
  *           (C) 2006 Alexey Proskuryakov (ap@nypop.com)
  * Copyright (C) 2007 Samuel Weinig (sam@webkit.org)
  * Copyright (C) 2010 Google Inc. All rights reserved.
  * Copyright (C) 2008 Torch Mobile Inc. All rights reserved. (http://www.torchmobile.com/)
  * Copyright (C) 2012 Samsung Electronics. All rights reserved.
@@ skipping 1467 matching lines @@
 {
     if (!m_hasNonEmptyList)
         return 0;
 
     if (!m_inputType->shouldRespectListAttribute())
         return 0;
 
     Element* element = treeScope().getElementById(fastGetAttribute(listAttr));
     if (!element)
         return 0;
-    if (!element->hasTagName(datalistTag))
+    if (!isHTMLDataListElement(*element))
         return 0;
 
     return toHTMLDataListElement(element);
 }
 
 bool HTMLInputElement::hasValidDataListOptions() const
 {
     HTMLDataListElement* dataList = this->dataList();
     if (!dataList)
         return false;
@@ skipping 369 matching lines @@
 }
 
 #if ENABLE(INPUT_MULTIPLE_FIELDS_UI)
 PassRefPtr<RenderStyle> HTMLInputElement::customStyleForRenderer()
 {
     return m_inputTypeView->customStyleForRenderer(originalStyleForRenderer());
 }
 #endif
 
 } // namespace