Have ElementTraversal::firstWithin() take a reference

Source/core/dom/ContainerNode.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 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 874 matching lines @@
     }
 }
 
 PassRefPtr<HTMLCollection> ContainerNode::children()
 {
     return ensureRareData().ensureNodeLists().addCacheWithAtomicName<HTMLCollection>(this, NodeChildren);
 }
 
 Element* ContainerNode::firstElementChild() const
 {
-    return ElementTraversal::firstWithin(this);
+    return ElementTraversal::firstWithin(*this);
 }
 
 Element* ContainerNode::lastElementChild() const
 {
     Node* n = lastChild();
     while (n && !n->isElementNode())
         n = n->previousSibling();
     return toElement(n);
 }
 
@@ skipping 98 matching lines @@
         return true;
 
     if (node->isElementNode() && toElement(node)->shadow())
         return true;
 
     return false;
 }
 #endif
 
 } // namespace WebCore