Make it clear a DocumentNameCollection can only contain HTMLElements

Source/core/dom/Document.cpp

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 1999 Antti Koivisto (koivisto@kde.org)
  *           (C) 2001 Dirk Mueller (mueller@kde.org)
  *           (C) 2006 Alexey Proskuryakov (ap@webkit.org)
  * Copyright (C) 2004, 2005, 2006, 2007, 2008, 2009, 2011, 2012 Apple Inc. All rights reserved.
  * Copyright (C) 2008, 2009 Torch Mobile Inc. All rights reserved. (http://www.torchmobile.com/)
  * Copyright (C) 2008, 2009, 2011, 2012 Google Inc. All rights reserved.
  * Copyright (C) 2010 Nokia Corporation and/or its subsidiary(-ies)
  * Copyright (C) Research In Motion Limited 2010-2011. All rights reserved.
@@ skipping 4593 matching lines @@
 PassRefPtrWillBeRawPtr<HTMLAllCollection> Document::all()
 {
     return ensureCachedCollection<HTMLAllCollection>(DocAll);
 }
 
 PassRefPtrWillBeRawPtr<HTMLCollection> Document::windowNamedItems(const AtomicString& name)
 {
     return ensureCachedCollection<WindowNameCollection>(WindowNamedItems, name);
 }
 
-PassRefPtrWillBeRawPtr<HTMLCollection> Document::documentNamedItems(const AtomicString& name)
+PassRefPtrWillBeRawPtr<DocumentNameCollection> Document::documentNamedItems(const AtomicString& name)
 {
     return ensureCachedCollection<DocumentNameCollection>(DocumentNamedItems, name);
 }
 
 void Document::finishedParsing()
 {
     ASSERT(!scriptableDocumentParser() || !m_parser->isParsing());
     ASSERT(!scriptableDocumentParser() || m_readyState != Loading);
     setParsing(false);
     if (!m_documentTiming.domContentLoadedEventStart)
@@ skipping 1170 matching lines @@
 using namespace blink;
 void showLiveDocumentInstances()
 {
     WeakDocumentSet& set = liveDocumentSet();
     fprintf(stderr, "There are %u documents currently alive:\n", set.size());
     for (WeakDocumentSet::const_iterator it = set.begin(); it != set.end(); ++it) {
         fprintf(stderr, "- Document %p URL: %s\n", *it, (*it)->url().string().utf8().data());
     }
 }
 #endif