Use stricter typing for NodeLists throughout the code base

Source/core/html/HTMLFieldSetElement.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, 2010 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 10 matching lines @@
  * Boston, MA 02110-1301, USA.
  *
  */
 
 #include "config.h"
 #include "core/html/HTMLFieldSetElement.h"
 
 #include "core/HTMLNames.h"
 #include "core/dom/ElementTraversal.h"
 #include "core/html/HTMLCollection.h"
+#include "core/html/HTMLFormControlsCollection.h"
 #include "core/html/HTMLLegendElement.h"
 #include "core/html/HTMLObjectElement.h"
 #include "core/rendering/RenderFieldset.h"
 #include "wtf/StdLibExtras.h"
 
 namespace WebCore {
 
 using namespace HTMLNames;
 
 inline HTMLFieldSetElement::HTMLFieldSetElement(Document& document, HTMLFormElement* form)
@@ skipping 52 matching lines @@
 RenderObject* HTMLFieldSetElement::createRenderer(RenderStyle*)
 {
     return new RenderFieldset(this);
 }
 
 HTMLLegendElement* HTMLFieldSetElement::legend() const
 {
     return Traversal<HTMLLegendElement>::firstChild(*this);
 }
 
-PassRefPtrWillBeRawPtr<HTMLCollection> HTMLFieldSetElement::elements()
+PassRefPtrWillBeRawPtr<HTMLFormControlsCollection> HTMLFieldSetElement::elements()
 {
-    return ensureCachedHTMLCollection(FormControls);
+    return toHTMLFormControlsCollection(ensureCachedHTMLCollection(FormControls).get());
 }
 
 void HTMLFieldSetElement::refreshElementsIfNeeded() const
 {
     uint64_t docVersion = document().domTreeVersion();
     if (m_documentVersion == docVersion)
         return;
 
     m_documentVersion = docVersion;
 
@@ skipping 12 matching lines @@
     }
 }
 
 const FormAssociatedElement::List& HTMLFieldSetElement::associatedElements() const
 {
     refreshElementsIfNeeded();
     return m_associatedElements;
 }
 
 } // namespace