Don't try to find a slot in a v0 shadow tree.

third_party/WebKit/Source/core/dom/Node.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, 2010, 2011 Apple Inc. All rights reserved.
  * Copyright (C) 2008 Nokia Corporation and/or its subsidiary(-ies)
  * Copyright (C) 2009 Torch Mobile Inc. All rights reserved. (http://www.torchmobile.com/)
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Library General Public
@@ skipping 2244 matching lines @@
         if (!insertionPoint->containingShadowRoot()->isOpenOrV0())
             break;
         filteredInsertionPoints.append(insertionPoint);
     }
     return StaticNodeList::adopt(filteredInsertionPoints);
 }
 
 HTMLSlotElement* Node::assignedSlot() const
 {
     ASSERT(!needsDistributionRecalc());
-    if (ElementShadow* shadow = parentElementShadow())
-        return shadow->assignedSlotFor(*this);
+    if (ElementShadow* shadow = parentElementShadow()) {
+        if (shadow->isV1())
+            return shadow->assignedSlotFor(*this);
+    }
     return nullptr;
 }
 
 HTMLSlotElement* Node::assignedSlotForBinding()
 {
     updateDistribution();
     if (ElementShadow* shadow = parentElementShadow()) {
         if (shadow->isV1() && shadow->isOpenOrV0())
             return shadow->assignedSlotFor(*this);
     }
@@ skipping 148 matching lines @@
 
 void showNodePath(const blink::Node* node)
 {
     if (node)
         node->showNodePathForThis();
     else
         fprintf(stderr, "Cannot showNodePath for (nil)\n");
 }
 
 #endif