Have HTMLCollection::item() return an Element as per specification

Source/core/html/HTMLAllCollection.cpp

 /*
  * Copyright (C) 2009, 2011, 2012 Apple Inc. All rights reserved.
  *
  * 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
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
@@ skipping 28 matching lines @@
 HTMLAllCollection::HTMLAllCollection(ContainerNode* node, CollectionType type)
     : HTMLCollection(node, type, DoesNotOverrideItemAfter)
 {
     ScriptWrappable::init(this);
 }
 
 HTMLAllCollection::~HTMLAllCollection()
 {
 }
 
-Node* HTMLAllCollection::namedItemWithIndex(const AtomicString& name, unsigned index) const
+Element* HTMLAllCollection::namedItemWithIndex(const AtomicString& name, unsigned index) const
 {
     updateNameCache();
 
     if (Vector<Element*>* cache = idCache(name)) {
         if (index < cache->size())
             return cache->at(index);
         index -= cache->size();
     }
 
     if (Vector<Element*>* cache = nameCache(name)) {
@@ skipping 23 matching lines @@
     returnValue0Enabled = true;
     returnValue0 = NamedNodesCollection::create(namedItems);
 }
 
 PassRefPtr<HTMLCollection> HTMLAllCollection::tags(const AtomicString& name)
 {
     return ownerNode()->getElementsByTagName(name);
 }
 
 } // namespace WebCore