Make sure the rootNode of a LiveNodeListBase is always a ContainerNode

Source/core/dom/ClassNodeList.h

Index: Source/core/dom/ClassNodeList.h
diff --git a/Source/core/dom/ClassNodeList.h b/Source/core/dom/ClassNodeList.h
index a1dcbf4571846cbd4414f487557a0c0ab1e6c7e1..38704dacbb1b1e9bb3d0a691dfac21d3e6aad0d7 100644
--- a/Source/core/dom/ClassNodeList.h
+++ b/Source/core/dom/ClassNodeList.h
@@ -41,7 +41,7 @@ class ClassNodeList FINAL : public LiveNodeList {
 public:
     // classNames argument is an AtomicString because it is common for Elements to share the same class names.
     // It is also used to construct a SpaceSplitString (m_classNames) and its constructor requires an AtomicString.
-    static PassRefPtr<ClassNodeList> create(PassRefPtr<Node> rootNode, CollectionType type, const AtomicString& classNames)
+    static PassRefPtr<ClassNodeList> create(PassRefPtr<ContainerNode> rootNode, CollectionType type, const AtomicString& classNames)
     {
         ASSERT_UNUSED(type, type == ClassNodeListType);
         return adoptRef(new ClassNodeList(rootNode, classNames));
@@ -52,7 +52,7 @@ public:
     bool nodeMatchesInlined(Element*) const;
 
 private:
-    ClassNodeList(PassRefPtr<Node> rootNode, const AtomicString& classNames);
+    ClassNodeList(PassRefPtr<ContainerNode> rootNode, const AtomicString& classNames);
 
     virtual bool nodeMatches(Element*) const OVERRIDE;