Only allow one shadowRoot.

sky/engine/core/dom/shadow/ComposedTreeWalker.h

 /*
  * Copyright (C) 2012 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Neither the name of Google Inc. nor the names of its
@@ skipping 87 matching lines @@
 
     static Node* traverseNextSibling(const Node*);
     static Node* traversePreviousSibling(const Node*);
 
     static Node* traverseSiblingOrBackToInsertionPoint(const Node*, TraversalDirection);
     static Node* traverseSiblingInCurrentTree(const Node*, TraversalDirection);
 
     static Node* traverseSiblings(const Node*, TraversalDirection);
     static Node* traverseDistributedNodes(const Node*, const InsertionPoint*, TraversalDirection);
 
-    static Node* traverseBackToYoungerShadowRoot(const Node*, TraversalDirection);
-
     Node* traverseParentOrHost(const Node*) const;
 
     RawPtr<const Node> m_node;
 };
 
 inline ComposedTreeWalker::ComposedTreeWalker(const Node* node, StartPolicy startPolicy)
     : m_node(node)
 {
 #if ENABLE(ASSERT)
     if (m_node && startPolicy == CannotStartFromShadowBoundary)
@@ skipping 86 matching lines @@
 
 inline Node* ComposedTreeWalker::traverseLastChild(const Node* node) const
 {
     ASSERT(node);
     return traverseChild(node, TraversalDirectionBackward);
 }
 
 } // namespace
 
 #endif  // SKY_ENGINE_CORE_DOM_SHADOW_COMPOSEDTREEWALKER_H_