Use stricter typing for NodeLists throughout the code base

Source/core/html/LabelableElement.h

 /*
  * Copyright (C) 2012 Google 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:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 17 matching lines @@
  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  */
 
 #ifndef LabelableElement_h
 #define LabelableElement_h
 
 #include "core/html/HTMLElement.h"
 
 namespace WebCore {
 
+class LabelsNodeList;
+
 // LabelableElement represents "labelable element" defined in the HTML
 // specification, and provides the implementation of the "labels" attribute.
 class LabelableElement : public HTMLElement {
 public:
     virtual ~LabelableElement();
-    PassRefPtrWillBeRawPtr<NodeList> labels();
+    PassRefPtrWillBeRawPtr<LabelsNodeList> labels();
     virtual bool supportLabels() const { return false; }
 
     virtual void trace(Visitor*) OVERRIDE;
 
 protected:
     LabelableElement(const QualifiedName& tagName, Document&);
 
 private:
     virtual bool isLabelable() const OVERRIDE FINAL { return true; }
 };
 
 inline bool isLabelableElement(const Element& element)
 {
     return element.isHTMLElement() && toHTMLElement(element).isLabelable();
 }
 
 inline bool isLabelableElement(const HTMLElement& element)
 {
     return element.isLabelable();
 }
 
 DEFINE_HTMLELEMENT_TYPE_CASTS_WITH_FUNCTION(LabelableElement);
 
 } // namespace WebCore
 
 #endif