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

Source/core/dom/custom/CustomElementMicrotaskResolutionStep.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:
  *
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
@@ skipping 37 matching lines @@
 {
 }
 
 CustomElementMicrotaskResolutionStep::~CustomElementMicrotaskResolutionStep()
 {
 }
 
 CustomElementMicrotaskStep::Result CustomElementMicrotaskResolutionStep::process()
 {
     m_context->resolve(m_element.get(), m_descriptor);
-    return CustomElementMicrotaskStep::Continue;
+    return CustomElementMicrotaskStep::ContinueWithRemoving;
 }
 
 #if !defined(NDEBUG)
 void CustomElementMicrotaskResolutionStep::show(unsigned indent)
 {
-    fprintf(stderr, "indent: %d\n", indent);
     fprintf(stderr, "%*sResolution: ", indent, "");
     m_element->outerHTML().show();
 }
 #endif
 
 } // namespace WebCore