Make sure the rootNode of a LiveNodeListBase is always a ContainerNode

Source/core/html/HTMLFormControlsCollection.h

 /*
  * Copyright (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 1999 Antti Koivisto (koivisto@kde.org)
  * Copyright (C) 2003, 2004, 2005, 2006, 2007, 2008 Apple Inc. All rights reserved.
  *
  * 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
  * version 2 of the License, or (at your option) any later version.
  *
@@ skipping 20 matching lines @@
 class FormAssociatedElement;
 class HTMLElement;
 class HTMLImageElement;
 class QualifiedName;
 
 // This class is just a big hack to find form elements even in malformed HTML elements.
 // The famous <table><tr><form><td> problem.
 
 class HTMLFormControlsCollection FINAL : public HTMLCollection {
 public:
-    static PassRefPtr<HTMLFormControlsCollection> create(Node*, CollectionType);
+    static PassRefPtr<HTMLFormControlsCollection> create(ContainerNode*, CollectionType);
 
     virtual ~HTMLFormControlsCollection();
 
     virtual Node* namedItem(const AtomicString& name) const OVERRIDE;
     void namedGetter(const AtomicString& name, bool&, RefPtr<RadioNodeList>&, bool&, RefPtr<Node>&);
 
 private:
-    explicit HTMLFormControlsCollection(Node*);
+    explicit HTMLFormControlsCollection(ContainerNode*);
 
     virtual void updateNameCache() const OVERRIDE;
 
     const Vector<FormAssociatedElement*>& formControlElements() const;
     const Vector<HTMLImageElement*>& formImageElements() const;
     virtual Element* virtualItemAfter(Element*) const OVERRIDE;
     virtual void invalidateCache() const OVERRIDE;
 
     mutable Element* m_cachedElement;
     mutable unsigned m_cachedElementOffsetInArray;
 };
 
 } // namespace
 
 #endif