Make HTMLCollection / NodeList backward traversal consistent with forward one

Source/core/dom/LiveNodeList.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, 2006, 2007, 2008, 2010 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 22 matching lines @@
 Node* LiveNodeList::virtualOwnerNode() const
 {
     return &ownerNode();
 }
 
 void LiveNodeList::invalidateCache(Document*) const
 {
     m_collectionIndexCache.invalidate();
 }
 
-Element* LiveNodeList::itemBefore(const Element* previous) const
-{
-    return LiveNodeListBase::itemBefore(*this, previous);
-}
-
 Element* LiveNodeList::traverseToFirstElement() const
 {
     return firstMatchingElement(*this);
 }
 
+Element* LiveNodeList::traverseToLastElement() const
+{
+    return lastMatchingElement(*this);
+}
+
 Element* LiveNodeList::traverseForwardToOffset(unsigned offset, Element& currentNode, unsigned& currentOffset) const
 {
     return traverseMatchingElementsForwardToOffset(*this, offset, currentNode, currentOffset);
 }
 
+Element* LiveNodeList::traverseBackwardToOffset(unsigned offset, Element& currentNode, unsigned& currentOffset) const
+{
+    return traverseMatchingElementsBackwardToOffset(*this, offset, currentNode, currentOffset);
+}
+
 } // namespace WebCore