Introduce isHTMLLabelElement and toHTMLLabelElement

Source/core/dom/TreeScope.cpp

 /*
  * Copyright (C) 2011 Google Inc. All Rights Reserved.
  * Copyright (C) 2012 Apple Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
@@ skipping 249 matching lines @@
 
 HTMLLabelElement* TreeScope::labelElementForId(const AtomicString& forAttributeValue)
 {
     if (forAttributeValue.isEmpty())
         return 0;
 
     if (!m_labelsByForAttribute) {
         // Populate the map on first access.
         m_labelsByForAttribute = adoptPtr(new DocumentOrderedMap);
         for (Element* element = ElementTraversal::firstWithin(rootNode()); element; element = ElementTraversal::next(element)) {
-            if (element->hasTagName(labelTag)) {
-                HTMLLabelElement* label = static_cast<HTMLLabelElement*>(element);
+            if (isHTMLLabelElement(element)) {
+                HTMLLabelElement* label = toHTMLLabelElement(element);
                 const AtomicString& forValue = label->fastGetAttribute(forAttr);
                 if (!forValue.isEmpty())
                     addLabel(forValue, label);
             }
         }
     }
 
-    return static_cast<HTMLLabelElement*>(m_labelsByForAttribute->getElementByLabelForAttribute(forAttributeValue.impl(), this));
+    return toHTMLLabelElement(m_labelsByForAttribute->getElementByLabelForAttribute(forAttributeValue.impl(), this));
 }
 
 DOMSelection* TreeScope::getSelection() const
 {
     if (!rootNode()->document()->frame())
         return 0;
 
     if (m_selection)
         return m_selection.get();
 
@@ skipping 198 matching lines @@
 {
     ASSERT(scope);
     for (; scope; scope = scope->parentTreeScope()) {
         if (scope == this)
             return true;
     }
     return false;
 }
 
 } // namespace WebCore