Some speculation about making opaque root finding cheaper.

third_party/WebKit/Source/core/dom/Node.cpp

Index: third_party/WebKit/Source/core/dom/Node.cpp
diff --git a/third_party/WebKit/Source/core/dom/Node.cpp b/third_party/WebKit/Source/core/dom/Node.cpp
index 8983f821c4c68e0a9ee2ade29d6467b4f949a659..ab040f51bcd7f8f8fcd1c8904416013606a5f61a 100644
--- a/third_party/WebKit/Source/core/dom/Node.cpp
+++ b/third_party/WebKit/Source/core/dom/Node.cpp
@@ -1086,8 +1086,10 @@ Element* Node::parentOrShadowHostElement() const {
   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();
 }