Have NodeTraversal::previous*() take a reference

Source/core/rendering/RenderListItem.cpp

 /**
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 1999 Antti Koivisto (koivisto@kde.org)
  * Copyright (C) 2003, 2004, 2005, 2006, 2010 Apple Inc. All rights reserved.
  * Copyright (C) 2006 Andrew Wellington (proton@wiretapped.net)
  *
  * 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 132 matching lines @@
         current = ElementTraversal::nextIncludingPseudo(current, listNode);
     }
 
     return 0;
 }
 
 // Returns the previous list item with respect to the DOM order.
 static RenderListItem* previousListItem(const Node* listNode, const RenderListItem* item)
 {
     Node* current = item->node();
-    for (current = ElementTraversal::previousIncludingPseudo(current, listNode); current; current = ElementTraversal::previousIncludingPseudo(current, listNode)) {
+    ASSERT(current);
+    for (current = ElementTraversal::previousIncludingPseudo(*current, listNode); current; current = ElementTraversal::previousIncludingPseudo(*current, listNode)) {
         RenderObject* renderer = current->renderer();
         if (!renderer || (renderer && !renderer->isListItem()))
             continue;
         Node* otherList = enclosingList(toRenderListItem(renderer));
         // This item is part of our current list, so it's what we're looking for.
         if (listNode == otherList)
             return toRenderListItem(renderer);
         // We found ourself inside another list; lets skip the rest of it.
         // Use nextIncludingPseudo() here because the other list itself may actually
         // be a list item itself. We need to examine it, so we do this to counteract
@@ skipping 351 matching lines @@
             // assume that all the following ones have too.
             // This gives us the opportunity to stop here and avoid
             // marking the same nodes again.
             break;
         }
         item->updateValue();
     }
 }
 
 } // namespace WebCore