Move Node::lastDescendantOrSelf() to NodeTraversal and rename to lastWithinOrSelf()

Source/core/dom/NodeTraversal.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, 2010, 2011, 2012 Apple Inc. All rights reserved.
  * Copyright (C) 2008, 2009 Torch Mobile Inc. All rights reserved. (http://www.torchmobile.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 86 matching lines @@
 }
 
 Node* NodeTraversal::lastWithin(const ContainerNode& current)
 {
     Node* descendant = current.lastChild();
     for (Node* child = descendant; child; child = child->lastChild())
         descendant = child;
     return descendant;
 }
 
+Node& NodeTraversal::lastWithinOrSelf(Node& current)
+{
+    Node* lastDescendant = current.isContainerNode() ? NodeTraversal::lastWithin(toContainerNode(current)) : 0;
+    return lastDescendant ? *lastDescendant : current;
+}
+
 Node* NodeTraversal::previous(const Node& current, const Node* stayWithin)
 {
     if (current == stayWithin)
         return 0;
     if (current.previousSibling()) {
         Node* previous = current.previousSibling();
         while (Node* child = previous->lastChild())
             previous = child;
         return previous;
     }
@@ skipping 44 matching lines @@
     if (Node* lastChild = current.lastChild())
         return lastChild;
     if (current == stayWithin)
         return 0;
     if (current.previousSibling())
         return current.previousSibling();
     return previousAncestorSiblingPostOrder(current, stayWithin);
 }
 
 } // namespace blink