Get rid of TreeBoundaryCrossingRules.

Source/core/dom/shadow/ShadowRoot.cpp

Index: Source/core/dom/shadow/ShadowRoot.cpp
diff --git a/Source/core/dom/shadow/ShadowRoot.cpp b/Source/core/dom/shadow/ShadowRoot.cpp
index 79445bdca87a62a1c8755efad57944da994e67ca..cc11940754493fe7b35824095abace4819567909 100644
--- a/Source/core/dom/shadow/ShadowRoot.cpp
+++ b/Source/core/dom/shadow/ShadowRoot.cpp
@@ -155,6 +155,12 @@ void ShadowRoot::attach(const AttachContext& context)
     DocumentFragment::attach(context);
 }
 
+void ShadowRoot::detach(const AttachContext& context)
+{
+    TreeScope::clearComposedParent();
+    DocumentFragment::detach(context);
+}
+
 Node::InsertionNotificationRequest ShadowRoot::insertedInto(ContainerNode* insertionPoint)
 {
     DocumentFragment::insertedInto(insertionPoint);