REGRESSION(r171966): Custom elements in async imports don't get upgrade.

Source/core/html/imports/HTMLImportChild.cpp

 /*
  * Copyright (C) 2013 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 77 matching lines @@
 
     ensureLoader();
 }
 
 void HTMLImportChild::didFinish()
 {
     if (m_client)
         m_client->didFinish();
 }
 
-static bool hasAsyncImportAncestor(HTMLImport* import)
-{
-    for (HTMLImport* i = import; i; i = i->parent()) {
-        if (!i->isSync())
-            return true;
-    }
-
-    return false;
-}
-
 void HTMLImportChild::didFinishLoading()
 {
     clearResource();
     stateWillChange();
     if (m_customElementMicrotaskStep)
         CustomElementMicrotaskDispatcher::instance().importDidFinish(m_customElementMicrotaskStep.get());
-    // FIXME(crbug.com/365956):
-    // This is needed because async import currently never consumes the queue and
-    // it prevents the children of such an async import from finishing.
-    // Their steps are never processed.
-    // Although this is clearly not the right fix,
-    // https://codereview.chromium.org/249563003/ should get rid of this part.
-    if (hasAsyncImportAncestor(this))
-        didFinishUpgradingCustomElements();
 }
 
 void HTMLImportChild::didFinishUpgradingCustomElements()
 {
     stateWillChange();
     m_customElementMicrotaskStep.clear();
 }
 
 bool HTMLImportChild::isLoaded() const
 {
@@ skipping 39 matching lines @@
 void HTMLImportChild::ensureLoader()
 {
     if (m_loader)
         return;
 
     if (HTMLImportChild* found = toHTMLImportsController(root())->findLinkFor(m_url, this))
         shareLoader(found);
     else
         createLoader();
 
-    if (isSync() && !isDone()) {
+    if (!isDone() && !formsCycle()) {
         ASSERT(!m_customElementMicrotaskStep);
         m_customElementMicrotaskStep = CustomElement::didCreateImport(this)->weakPtr();
     }
 }
 
 void HTMLImportChild::createLoader()
 {
     ASSERT(!m_loader);
     m_loader = toHTMLImportsController(root())->createLoader();
     m_loader->addImport(this);
@@ skipping 46 matching lines @@
     HTMLImport::showThis();
     fprintf(stderr, " loader=%p step=%p sync=%s url=%s",
         m_loader,
         m_customElementMicrotaskStep.get(),
         isSync() ? "Y" : "N",
         url().string().utf8().data());
 }
 #endif
 
 } // namespace WebCore