Only allow one shadowRoot.

sky/engine/core/dom/shadow/InsertionPoint.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.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 77 matching lines @@
 inline bool isActiveInsertionPoint(const Node& node)
 {
     return node.isInsertionPoint() && toInsertionPoint(node).isActive();
 }
 
 inline ElementShadow* shadowWhereNodeCanBeDistributed(const Node& node)
 {
     Node* parent = node.parentNode();
     if (!parent)
         return 0;
-    if (parent->isShadowRoot() && !toShadowRoot(parent)->isYoungest())
-        return node.shadowHost()->shadow();
     if (isActiveInsertionPoint(*parent))
         return node.shadowHost()->shadow();
     if (parent->isElementNode())
         return toElement(parent)->shadow();
     return 0;
 }
 
 const InsertionPoint* resolveReprojection(const Node*);
 
 void collectDestinationInsertionPoints(const Node&, Vector<RawPtr<InsertionPoint>, 8>& results);
 
 } // namespace blink
 
 #endif  // SKY_ENGINE_CORE_DOM_SHADOW_INSERTIONPOINT_H_