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

Source/core/html/HTMLAreaElement.cpp

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 1999 Antti Koivisto (koivisto@kde.org)
  * Copyright (C) 2004, 2005, 2006, 2009, 2011 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 163 matching lines @@
         case Unknown:
             break;
     }
 
     return path;
 }
 
 HTMLImageElement* HTMLAreaElement::imageElement() const
 {
     Element* mapElement = parentElement();
-    while (mapElement && !mapElement->hasTagName(mapTag))
+    while (mapElement && !isHTMLMapElement(*mapElement))
         mapElement = mapElement->parentElement();
 
     if (!mapElement)
         return 0;
 
-    return toHTMLMapElement(mapElement)->imageElement();
+    return toHTMLMapElement(*mapElement).imageElement();
 }
 
 bool HTMLAreaElement::isKeyboardFocusable() const
 {
     return isFocusable();
 }
 
 bool HTMLAreaElement::isMouseFocusable() const
 {
     return isFocusable();
@@ skipping 39 matching lines @@
 }
 
 bool HTMLAreaElement::supportsFocus() const
 {
     // If the AREA element was a link, it should support focus.
     // FIXME: This means that an AREA that is not a link cannot be made focusable through contenteditable or tabindex. Is it correct?
     return isLink();
 }
 
 }