[ServiceWorker] Allow waitUntil to be called multiple times asynchronously

third_party/WebKit/Source/modules/serviceworkers/ExtendableEvent.h

 /*
  * Copyright (C) 2014 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 45 matching lines @@
 
   const AtomicString& InterfaceName() const override;
   DECLARE_VIRTUAL_TRACE();
 
  protected:
   ExtendableEvent(const AtomicString& type, const ExtendableEventInit&);
   ExtendableEvent(const AtomicString& type,
                   const ExtendableEventInit&,
                   WaitUntilObserver*);
 
+  const bool created_by_script_;
   Member<WaitUntilObserver> observer_;
 };
 
 }  // namespace blink
 
 #endif  // ExtendableEvent_h