Make sure the rootNode of a LiveNodeListBase is always a ContainerNode

Source/core/html/HTMLFormControlsCollection.h

Index: Source/core/html/HTMLFormControlsCollection.h
diff --git a/Source/core/html/HTMLFormControlsCollection.h b/Source/core/html/HTMLFormControlsCollection.h
index e9f1f33e4512f67d2e0013e9cda39d7e33db35c5..7ce6436fe19b8615e0785b7671c2db85eda9d581 100644
--- a/Source/core/html/HTMLFormControlsCollection.h
+++ b/Source/core/html/HTMLFormControlsCollection.h
@@ -38,7 +38,7 @@ class QualifiedName;
 
 class HTMLFormControlsCollection FINAL : public HTMLCollection {
 public:
-    static PassRefPtr<HTMLFormControlsCollection> create(Node*, CollectionType);
+    static PassRefPtr<HTMLFormControlsCollection> create(ContainerNode*, CollectionType);
 
     virtual ~HTMLFormControlsCollection();
 
@@ -46,7 +46,7 @@ public:
     void namedGetter(const AtomicString& name, bool&, RefPtr<RadioNodeList>&, bool&, RefPtr<Node>&);
 
 private:
-    explicit HTMLFormControlsCollection(Node*);
+    explicit HTMLFormControlsCollection(ContainerNode*);
 
     virtual void updateNameCache() const OVERRIDE;