Remove unused WorkerGlobalScope::m_workerObservers HashSet

Source/core/workers/WorkerGlobalScope.h

 /*
  * Copyright (C) 2008, 2009 Apple 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
  *    notice, this list of conditions and the following disclaimer in the
@@ skipping 138 matching lines @@
         mutable RefPtr<WorkerConsole> m_console;
         mutable RefPtr<WorkerLocation> m_location;
         mutable RefPtr<WorkerNavigator> m_navigator;
 
         OwnPtr<WorkerScriptController> m_script;
         WorkerThread* m_thread;
 
         OwnPtr<WorkerInspectorController> m_workerInspectorController;
         bool m_closing;
 
-        HashSet<Observer*> m_workerObservers;
-
         OwnPtr<WorkerEventQueue> m_eventQueue;
 
         OwnPtr<WorkerClients> m_workerClients;
 
         double m_timeOrigin;
     };
 
 DEFINE_TYPE_CASTS(WorkerGlobalScope, ExecutionContext, context, context->isWorkerGlobalScope(), context.isWorkerGlobalScope());
 
 } // namespace WebCore
 
 #endif // WorkerGlobalScope_h