Some speculation about making opaque root finding cheaper.

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/)
  *
@@ skipping 1068 matching lines @@
 
   if (parent->isShadowRoot())
     return &toShadowRoot(parent)->host();
 
   if (!parent->isElementNode())
     return nullptr;
 
   return toElement(parent);
 }
 
-ContainerNode* Node::parentOrShadowHostOrTemplateHostNode() const {
-  if (isDocumentFragment() && toDocumentFragment(this)->isTemplateContent())
+ContainerNode* Node::parentOrShadowHostOrTemplateHostNodeForDocumentFragment()
+    const {
+  DCHECK(isDocumentFragment() && !isShadowRoot());
+  if (toDocumentFragment(this)->isTemplateContent())
     return static_cast<const TemplateContentDocumentFragment*>(this)->host();
   return parentOrShadowHostNode();
 }
 
 Document* Node::ownerDocument() const {
   Document* doc = &document();
   return doc == this ? nullptr : doc;
 }
 
 const KURL& Node::baseURI() const {
@@ skipping 1386 matching lines @@
   if (node) {
     std::stringstream stream;
     node->printNodePathTo(stream);
     LOG(INFO) << stream.str();
   } else {
     LOG(INFO) << "Cannot showNodePath for <null>";
   }
 }
 
 #endif