Have NodeList::item() overrides return an Element* when appropriate

Source/core/dom/LiveNodeList.h

 /*
  * 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 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 24 matching lines @@
 
 class Element;
 
 class LiveNodeList : public NodeList, public LiveNodeListBase {
     WILL_BE_USING_GARBAGE_COLLECTED_MIXIN(LiveNodeList);
 public:
     LiveNodeList(ContainerNode& ownerNode, CollectionType collectionType, NodeListInvalidationType invalidationType, NodeListRootType rootType = NodeListIsRootedAtNode)
         : LiveNodeListBase(ownerNode, rootType, invalidationType, collectionType) { }
 
     virtual unsigned length() const OVERRIDE FINAL { return m_collectionIndexCache.nodeCount(*this); }
-    virtual Node* item(unsigned offset) const OVERRIDE FINAL { return m_collectionIndexCache.nodeAt(*this, offset); }
+    virtual Element* item(unsigned offset) const OVERRIDE FINAL { return m_collectionIndexCache.nodeAt(*this, offset); }
     virtual bool elementMatches(const Element&) const = 0;
 
     virtual void invalidateCache(Document* oldDocument = 0) const OVERRIDE FINAL;
     void invalidateCacheForAttribute(const QualifiedName*) const;
 
     bool shouldOnlyIncludeDirectChildren() const { return false; }
 
     // Collection IndexCache API.
     bool canTraverseBackward() const { return true; }
     Element* traverseToFirstElement() const;
@@ skipping 13 matching lines @@
 
 inline void LiveNodeList::invalidateCacheForAttribute(const QualifiedName* attrName) const
 {
     if (!attrName || shouldInvalidateTypeOnAttributeChange(invalidationType(), *attrName))
         invalidateCache();
 }
 
 } // namespace WebCore
 
 #endif // LiveNodeList_h