Have ElementTraversal / NodeTraversal's next() methods take a reference

Source/core/html/HTMLCollection.h

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 1999 Antti Koivisto (koivisto@kde.org)
  * Copyright (C) 2003, 2004, 2005, 2006, 2007, 2008, 2011, 2012 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 44 matching lines @@
         if (isLengthCacheValid())
             return cachedLength() == 1;
         if (isItemCacheValid())
             return cachedItem() && !cachedItemOffset() && !item(1);
         return item(0) && !item(1);
     }
 
     virtual Element* virtualItemAfter(unsigned& offsetInArray, Element*) const;
 
     Element* traverseFirstElement(unsigned& offsetInArray, ContainerNode* root) const;
-    Element* traverseForwardToOffset(unsigned offset, Element* currentElement, unsigned& currentOffset, unsigned& offsetInArray, ContainerNode* root) const;
+    Element* traverseForwardToOffset(unsigned offset, Element& currentElement, unsigned& currentOffset, unsigned& offsetInArray, ContainerNode* root) const;
 
 protected:
     HTMLCollection(Node* base, CollectionType, ItemAfterOverrideType);
 
     virtual void updateNameCache() const;
 
     typedef HashMap<StringImpl*, OwnPtr<Vector<Element*> > > NodeCacheMap;
     Vector<Element*>* idCache(const AtomicString& name) const { return m_idCache.get(name.impl()); }
     Vector<Element*>* nameCache(const AtomicString& name) const { return m_nameCache.get(name.impl()); }
     void appendIdCache(const AtomicString& name, Element* element) const { append(m_idCache, name, element); }
     void appendNameCache(const AtomicString& name, Element* element) const { append(m_nameCache, name, element); }
 
 private:
     bool checkForNameMatch(Element*, bool checkName, const AtomicString& name) const;
-    Element* traverseNextElement(unsigned& offsetInArray, Element* previous, ContainerNode* root) const;
+    Element* traverseNextElement(unsigned& offsetInArray, Element& previous, ContainerNode* root) const;
 
     virtual bool isLiveNodeList() const OVERRIDE { ASSERT_NOT_REACHED(); return true; }
 
     static void append(NodeCacheMap&, const AtomicString&, Element*);
 
     mutable NodeCacheMap m_idCache;
     mutable NodeCacheMap m_nameCache;
     mutable unsigned m_cachedElementsArrayOffset;
 
     friend class LiveNodeListBase;
 };
 
 } // namespace
 
 #endif