Use stricter typing for NodeLists throughout the code base

Source/core/html/HTMLFormElement.cpp

 /*
  * 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, 2005, 2006, 2007, 2008, 2009 Apple Inc. All rights reserved.
  *           (C) 2006 Alexey Proskuryakov (ap@nypop.com)
  *
  * 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
@@ skipping 541 matching lines @@
 #endif
 
 void HTMLFormElement::didAssociateByParser()
 {
     if (!m_didFinishParsingChildren)
         return;
     m_hasElementsAssociatedByParser = true;
     UseCounter::count(document(), UseCounter::FormAssociationByParser);
 }
 
-PassRefPtrWillBeRawPtr<HTMLCollection> HTMLFormElement::elements()
+PassRefPtrWillBeRawPtr<HTMLFormControlsCollection> HTMLFormElement::elements()
 {
-    return ensureCachedHTMLCollection(FormControls);
+    return toHTMLFormControlsCollection(ensureCachedHTMLCollection(FormControls).get());
 }
 
 void HTMLFormElement::collectAssociatedElements(Node& root, FormAssociatedElement::List& elements) const
 {
     elements.clear();
     for (HTMLElement* element = Traversal<HTMLElement>::firstWithin(root); element; element = Traversal<HTMLElement>::next(*element)) {
         FormAssociatedElement* associatedElement = 0;
         if (element->isFormControlElement())
             associatedElement = toHTMLFormControlElement(element);
         else if (isHTMLObjectElement(*element))
@@ skipping 223 matching lines @@
 }
 
 void HTMLFormElement::setDemoted(bool demoted)
 {
     if (demoted)
         UseCounter::count(document(), UseCounter::DemotedFormElement);
     m_wasDemoted = demoted;
 }
 
 } // namespace