Have ElementTraversal::firstWithin() take a reference

Source/core/dom/DocumentOrderedMap.cpp

 /*
  * Copyright (C) 2004, 2005, 2006, 2007, 2008, 2009 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:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 104 matching lines @@
 {
     ASSERT(key);
     ASSERT(scope);
 
     Element* element = m_map.get(key);
     if (element)
         return element;
 
     if (m_duplicateCounts.contains(key)) {
         // We know there's at least one node that matches; iterate to find the first one.
-        for (element = ElementTraversal::firstWithin(scope->rootNode()); element; element = ElementTraversal::next(*element)) {
+        ASSERT(scope->rootNode());
+        for (element = ElementTraversal::firstWithin(*scope->rootNode()); element; element = ElementTraversal::next(*element)) {
             if (!keyMatches(key, element))
                 continue;
             m_duplicateCounts.remove(key);
             m_map.set(key, element);
             return element;
         }
         ASSERT_NOT_REACHED();
     }
 
     return 0;
@@ skipping 13 matching lines @@
 {
     return get<keyMatchesLowercasedMapName>(key, scope);
 }
 
 Element* DocumentOrderedMap::getElementByLabelForAttribute(StringImpl* key, const TreeScope* scope) const
 {
     return get<keyMatchesLabelForAttribute>(key, scope);
 }
 
 } // namespace WebCore