[Oilpan] Apply RefCountedGarbageCollectedEventTarget on AbstractWorker

Source/core/workers/Worker.idl

 /*
  * Copyright (C) 2008, 2010 Apple Inc. All Rights Reserved.
  * Copyright (C) 2011 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 13 matching lines @@
  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  *
  */
 
 // https://html.spec.whatwg.org/#dedicated-workers-and-the-worker-interface
 
 [
     ActiveDOMObject,
     Constructor(DOMString scriptUrl),
     ConstructorCallWith=ExecutionContext,
+    GarbageCollected,
     // TODO(philipj): Exposed=(Window,Worker),
     RaisesException=Constructor,
 ] interface Worker : EventTarget {
     void terminate();
 
     // TODO(philipj): The SerializedScriptValue type should be any.
     [PostMessage, RaisesException] void postMessage(SerializedScriptValue message, optional sequence<Transferable> transfer);
     attribute EventHandler onmessage;
 };
 
 Worker implements AbstractWorker;