Make sure the rootNode of a LiveNodeListBase is always a ContainerNode

Source/core/html/LabelsNodeList.h

 /*
  * 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, 2007 Apple Inc. All rights reserved.
  * Copyright (C) 2010 Nokia 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
@@ skipping 14 matching lines @@
 #ifndef LabelsNodeList_h
 #define LabelsNodeList_h
 
 #include "core/dom/LiveNodeList.h"
 #include "wtf/PassRefPtr.h"
 
 namespace WebCore {
 
 class LabelsNodeList FINAL : public LiveNodeList {
 public:
-    static PassRefPtr<LabelsNodeList> create(Node* ownerNode, CollectionType type, const AtomicString&)
+    static PassRefPtr<LabelsNodeList> create(ContainerNode* ownerNode, CollectionType type, const AtomicString&)
     {
         ASSERT_UNUSED(type, type == LabelsNodeListType);
         return adoptRef(new LabelsNodeList(ownerNode));
     }
 
     virtual ~LabelsNodeList();
 
 protected:
-    explicit LabelsNodeList(Node*);
+    explicit LabelsNodeList(ContainerNode*);
 
     virtual bool nodeMatches(const Element&) const OVERRIDE;
 };
 
 } // namespace WebCore
 
 #endif // LabelsNodeList_h