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

Source/core/dom/custom/CustomElementMicrotaskDispatcher.cpp

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "config.h"
 #include "core/dom/custom/CustomElementMicrotaskDispatcher.h"
 
 #include "core/dom/Microtask.h"
 #include "core/dom/custom/CustomElementCallbackDispatcher.h"
 #include "core/dom/custom/CustomElementCallbackQueue.h"
@@ skipping 80 matching lines @@
     }
 
     m_elements.clear();
     CustomElementScheduler::microtaskDispatcherDidFinish();
     m_phase = Quiescent;
 }
 
 #if !defined(NDEBUG)
 void CustomElementMicrotaskDispatcher::show()
 {
-    m_resolutionAndImports->show(0);
+    fprintf(stderr, "Dispatcher:\n");
+    m_resolutionAndImports->show(1);
 }
 #endif
 
 } // namespace WebCore
 
 #if !defined(NDEBUG)
 void showCEMD()
 {
     WebCore::CustomElementMicrotaskDispatcher::instance().show();
 }
 #endif