Tentative: fix

Source/core/dom/TreeScopeAdopter.cpp

Index: Source/core/dom/TreeScopeAdopter.cpp
diff --git a/Source/core/dom/TreeScopeAdopter.cpp b/Source/core/dom/TreeScopeAdopter.cpp
index 79e17059048c5dbf33198255da7da9b516917ef7..dfef0255cbf1021499d867b452ba3bdaae2c8617 100644
--- a/Source/core/dom/TreeScopeAdopter.cpp
+++ b/Source/core/dom/TreeScopeAdopter.cpp
@@ -29,6 +29,7 @@
 #include "core/dom/Attr.h"
 #include "core/dom/NodeRareData.h"
 #include "core/dom/NodeTraversal.h"
+#include "core/dom/StyleEngine.h"
 #include "core/dom/shadow/ElementShadow.h"
 #include "core/dom/shadow/ShadowRoot.h"
 
@@ -137,10 +138,21 @@ inline void TreeScopeAdopter::moveNodeToNewDocument(Node& node, Document& oldDoc
             rareData->nodeLists()->adoptDocument(oldDocument, newDocument);
     }
 
+    ScopedStyleResolver* resolver = nullptr;
+    if (node.isShadowRoot()) {
+        resolver = node.treeScope().scopedStyleResolver();
+        // StyledScopeResolver may be null because it is lazily created.
+        if (resolver)
+            oldDocument.styleEngine()->removeScopedStyleResolver(resolver);
+    }
+
     oldDocument.moveNodeIteratorsToNewDocument(node, newDocument);
 
-    if (node.isShadowRoot())
+    if (node.isShadowRoot()) {
         toShadowRoot(node).setDocument(newDocument);
+        if (resolver)
+            newDocument.styleEngine()->addScopedStyleResolver(resolver);
+    }
 
 #if ENABLE(ASSERT)
     didMoveToNewDocumentWasCalled = false;