[TimeZoneMonitor] Decouple renderer side impl from content to blink.

third_party/WebKit/Source/core/workers/WorkerThread.h

 /*
  * Copyright (C) 2008 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 141 matching lines @@
 
   // Called for creating WorkerThreadLifecycleObserver on both the main thread
   // and the worker thread.
   WorkerThreadLifecycleContext* getWorkerThreadLifecycleContext() const {
     return m_workerThreadLifecycleContext;
   }
 
   // Number of active worker threads.
   static unsigned workerThreadCount();
 
+  // Returns a set of all worker threads. This must be called only on the main
+  // thread and the returned set must not be stored for future use.
+  static HashSet<WorkerThread*>& workerThreads();
+
   PlatformThreadId platformThreadId();
 
   bool isForciblyTerminated();
 
   void waitForShutdownForTesting() { m_shutdownEvent->wait(); }
 
  protected:
   WorkerThread(PassRefPtr<WorkerLoaderProxy>, WorkerReportingProxy&);
 
   // Factory method for creating a new worker context for the thread.
@@ skipping 117 matching lines @@
   // Scheduled when termination starts with TerminationMode::Force, and
   // cancelled when the worker thread is gracefully shut down.
   std::unique_ptr<ForceTerminationTask> m_scheduledForceTerminationTask;
 
   Persistent<WorkerThreadLifecycleContext> m_workerThreadLifecycleContext;
 };
 
 }  // namespace blink
 
 #endif  // WorkerThread_h