Use DEFINE_ELEMENT_TYPE_CASTS*() macros for Element subclasses

Source/core/html/HTMLLegendElement.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, 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 39 matching lines @@
 {
     // Check if there's a fieldset belonging to this legend.
     Element* fieldset = parentElement();
     while (fieldset && !fieldset->hasTagName(fieldsetTag))
         fieldset = fieldset->parentElement();
     if (!fieldset)
         return 0;
 
     // Find first form element inside the fieldset that is not a legend element.
     // FIXME: Should we consider tabindex?
-    Element* element = fieldset;
-    while ((element = ElementTraversal::next(*element, fieldset))) {
-        if (element->isFormControlElement())
-            return toHTMLFormControlElement(element);
-    }
-
-    return 0;
+    return Traversal<HTMLFormControlElement>::next(*fieldset, fieldset);
 }
 
 void HTMLLegendElement::focus(bool, FocusType type)
 {
     if (isFocusable())
         Element::focus(true, type);
 
     // To match other browsers' behavior, never restore previous selection.
     if (HTMLFormControlElement* control = associatedControl())
         control->focus(false, type);
@@ skipping 11 matching lines @@
     // its parent, then the form attribute must return the same value as the
     // form attribute on that fieldset element. Otherwise, it must return null.
     ContainerNode* fieldset = parentNode();
     if (!fieldset || !fieldset->hasTagName(fieldsetTag))
         return 0;
 
     return toHTMLFieldSetElement(fieldset)->formOwner();
 }
 
 } // namespace