Have NodeTraversal::previous*() take a reference

Source/core/xml/XPathStep.cpp

 /*
  * Copyright (C) 2005 Frerich Raabe <raabe@kde.org>
  * Copyright (C) 2006, 2009 Apple Inc. All rights reserved.
  * Copyright (C) 2007 Alexey Proskuryakov <ap@webkit.org>
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  *
  * 1. Redistributions of source code must retain the above copyright
@@ skipping 309 matching lines @@
                     }
                 }
             }
             return;
         case PrecedingAxis: {
             if (context->isAttributeNode())
                 context = toAttr(context)->ownerElement();
 
             Node* n = context;
             while (ContainerNode* parent = n->parentNode()) {
-                for (n = NodeTraversal::previous(n); n != parent; n = NodeTraversal::previous(n))
+                for (n = NodeTraversal::previous(*n); n != parent; n = NodeTraversal::previous(*n))
                     if (nodeMatches(n, PrecedingAxis, m_nodeTest))
                         nodes.append(n);
                 n = parent;
             }
             nodes.markSorted(false);
             return;
         }
         case AttributeAxis: {
             if (!context->isElementNode())
                 return;
@@ skipping 53 matching lines @@
             nodes.markSorted(false);
             return;
         }
     }
     ASSERT_NOT_REACHED();
 }
 
 
 }
 }