Make sure the rootNode of a LiveNodeListBase is always a ContainerNode

Source/core/html/HTMLCollection.h

Index: Source/core/html/HTMLCollection.h
diff --git a/Source/core/html/HTMLCollection.h b/Source/core/html/HTMLCollection.h
index be1f01d240c9fd9b5051d171865bae7532dbce89..077bf2acb0ac13b360e72a4d8ebcee61939c86b7 100644
--- a/Source/core/html/HTMLCollection.h
+++ b/Source/core/html/HTMLCollection.h
@@ -33,7 +33,7 @@ namespace WebCore {
 
 class HTMLCollection : public ScriptWrappable, public RefCounted<HTMLCollection>, public LiveNodeListBase {
 public:
-    static PassRefPtr<HTMLCollection> create(Node* base, CollectionType);
+    static PassRefPtr<HTMLCollection> create(ContainerNode* base, CollectionType);
     virtual ~HTMLCollection();
     virtual void invalidateCache() const OVERRIDE;
 
@@ -65,7 +65,7 @@ public:
     Element* traverseForwardToOffset(unsigned offset, Element& currentElement, unsigned& currentOffset, const ContainerNode& root) const;
 
 protected:
-    HTMLCollection(Node* base, CollectionType, ItemAfterOverrideType);
+    HTMLCollection(ContainerNode* base, CollectionType, ItemAfterOverrideType);
 
     virtual void updateNameCache() const;
     bool hasNameCache() const { return m_isNameCacheValid; }