Only allow reprojecting shadows between ShadowRoots of the same type

Source/core/html/shadow/HTMLShadowElement.cpp

 /*
  * Copyright (C) 2012 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 52 matching lines @@
     document()->updateDistributionForNodeIfNeeded(this);
 
     ShadowRoot* older = containingRoot->olderShadowRoot();
     if (!older || !older->shouldExposeToBindings() || older->insertionPoint() != this)
         return 0;
 
     ASSERT(older->shouldExposeToBindings());
     return older;
 }
 
-static inline Element* hostForOldestAuthorShadowRoot(ShadowRoot* root)
-{
-    return root && root->isOldestAuthorShadowRoot() ? root->host() : 0;
-}
-
-bool HTMLShadowElement::shouldSelect() const
-{
-    Element* host = hostForOldestAuthorShadowRoot(containingShadowRoot());
-    return !host || host->supportsShadowElementForUserAgentShadow();
-}
-
 Node::InsertionNotificationRequest HTMLShadowElement::insertedInto(ContainerNode* insertionPoint)
 {
-    if (insertionPoint->inDocument() && !shouldSelect()) {
-        String message = String::format("<shadow> doesn't work for %s element host.", containingShadowRoot()->host()->nodeName().utf8().data());
-        document()->addConsoleMessage(RenderingMessageSource, WarningMessageLevel, message);
+    if (insertionPoint->inDocument()) {
+        // Warn if trying to reproject between user agent and author shadows.
+        ShadowRoot* root = containingShadowRoot();
+        if (root && root->olderShadowRoot() && root->type() != root->olderShadowRoot()->type()) {
+            String message = String::format("<shadow> doesn't work for %s element host.", root->host()->tagName().utf8().data());
+            document()->addConsoleMessage(RenderingMessageSource, WarningMessageLevel, message);
+        }
     }
     return InsertionPoint::insertedInto(insertionPoint);
 }
 
 } // namespace WebCore