Only allow one shadowRoot.

sky/engine/core/dom/ContainerNode.cpp

 /*
  * 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, 2005, 2006, 2007, 2008, 2009, 2013 Apple 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
  * version 2 of the License, or (at your option) any later version.
@@ skipping 599 matching lines @@
 {
     EventDispatchForbiddenScope assertNoEventDispatch;
     ScriptForbiddenScope forbidScript;
 
     for (Node* node = &root; node; node = NodeTraversal::next(*node, &root)) {
         // As an optimization we don't notify leaf nodes when when inserting
         // into detached subtrees.
         if (!inDocument() && !node->isContainerNode())
             continue;
         node->insertedInto(this);
-        for (ShadowRoot* shadowRoot = node->youngestShadowRoot(); shadowRoot; shadowRoot = shadowRoot->olderShadowRoot())
+        if (ShadowRoot* shadowRoot = node->shadowRoot())
             notifyNodeInsertedInternal(*shadowRoot);
     }
 }
 
 void ContainerNode::notifyNodeRemoved(Node& root)
 {
     ScriptForbiddenScope forbidScript;
     EventDispatchForbiddenScope assertNoEventDispatch;
 
     for (Node* node = &root; node; node = NodeTraversal::next(*node, &root)) {
         // As an optimization we skip notifying Text nodes and other leaf nodes
         // of removal when they're not in the Document tree since the virtual
         // call to removedFrom is not needed.
         if (!node->inDocument() && !node->isContainerNode())
             continue;
         node->removedFrom(this);
-        for (ShadowRoot* shadowRoot = node->youngestShadowRoot(); shadowRoot; shadowRoot = shadowRoot->olderShadowRoot())
+        if (ShadowRoot* shadowRoot = node->shadowRoot())
             notifyNodeRemoved(*shadowRoot);
     }
 }
 
 void ContainerNode::attach(const AttachContext& context)
 {
     attachChildren(context);
     clearChildNeedsStyleRecalc();
     Node::attach(context);
 }
@@ skipping 297 matching lines @@
         return true;
 
     if (node->isElementNode() && toElement(node)->shadow())
         return true;
 
     return false;
 }
 #endif
 
 } // namespace blink