Minor cleanup for WorkerThread::stop

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 42 matching lines @@
 enum WorkerThreadStartMode {
     DontPauseWorkerGlobalScopeOnStart,
     PauseWorkerGlobalScopeOnStart
 };
 
 // TODO(sadrul): Rename to WorkerScript.
 class CORE_EXPORT WorkerThread : public RefCounted<WorkerThread> {
 public:
     virtual ~WorkerThread();
 
+    // Called on the main thread.

[Noel Gordon, 2015/06/11 07:07:03]

Is this true, or is this an implicit statement of how our system currently
works?  Also, can web workers start web workers?

[kinuko, 2015/06/11 08:59:44]

It just states how our system works today. Currently nested worker is not
supported in blink/chromium.

     virtual void start(PassOwnPtr<WorkerThreadStartupData>);
     virtual void stop();
 
     // Returns the thread this worker runs on. Some implementations can create
     // a new thread on the first call (e.g. shared, dedicated workers), whereas
     // some implementations can use an existing thread that is already being
     // used by other workers (e.g.  compositor workers).
     virtual WebThreadSupportingGC& backingThread() = 0;
 
     virtual void didStartRunLoop();
     virtual void didStopRunLoop();
 
     v8::Isolate* isolate() const { return m_isolate; }
 
     // Can be used to wait for this worker thread to shut down.
     // (This is signalled on the main thread, so it's assumed to be waited on the worker context thread)
     WebWaitableEvent* shutdownEvent() { return m_shutdownEvent.get(); }
 
     WebWaitableEvent* terminationEvent() { return m_terminationEvent.get(); }
+
+    // Called in shutdown sequence. Internally calls stop() (or stopInternal)
+    // and wait (by *blocking* the calling thread) until the worker(s) is/are
+    // shut down.
     void terminateAndWait();
     static void terminateAndWaitForAllWorkers();
 
     bool isCurrentThread();
     WorkerLoaderProxy* workerLoaderProxy() const
     {
         RELEASE_ASSERT(m_workerLoaderProxy);
         return m_workerLoaderProxy.get();
     }
 
     WorkerReportingProxy& workerReportingProxy() const { return m_workerReportingProxy; }
 
     void postTask(const WebTraceLocation&, PassOwnPtr<ExecutionContextTask>);
     void appendDebuggerTask(PassOwnPtr<WebThread::Task>);
 
     enum WaitMode { WaitForMessage, DontWaitForMessage };
     MessageQueueWaitResult runDebuggerTask(WaitMode = WaitForMessage);
 
     // These methods should be called if the holder of the thread is
     // going to call runDebuggerTask in a loop.
     void willEnterNestedLoop();
     void didLeaveNestedLoop();
 
     WorkerGlobalScope* workerGlobalScope() const { return m_workerGlobalScope.get(); }
+
+    // Returns true once stop() (or one of the terminate* methods which
+    // internally calls stop) is called.
     bool terminated();
 
     // Number of active worker threads.
     static unsigned workerThreadCount();
 
     PlatformThreadId platformThreadId();
 
     void interruptAndDispatchInspectorCommands();
     void setWorkerInspectorController(WorkerInspectorController*);
 
 protected:
     WorkerThread(PassRefPtr<WorkerLoaderProxy>, WorkerReportingProxy&);
 
     // Factory method for creating a new worker context for the thread.
     virtual PassRefPtrWillBeRawPtr<WorkerGlobalScope> createWorkerGlobalScope(PassOwnPtr<WorkerThreadStartupData>) = 0;
 
     virtual void postInitialize() { }
 
     virtual v8::Isolate* initializeIsolate();
     virtual void willDestroyIsolate();
     virtual void destroyIsolate();
     virtual void terminateV8Execution();
 
     // This is protected virtual for testing.
     virtual bool doIdleGc(double deadlineSeconds);
 
 private:
     friend class WorkerMicrotaskRunner;
 
-    void stopInShutdownSequence();
+    // Called on the main thread.
     void stopInternal();
 
+    // Called on the worker thread.
     void initialize(PassOwnPtr<WorkerThreadStartupData>);
     void shutdown();
     void performIdleWork(double deadlineSeconds);
     void postDelayedTask(const WebTraceLocation&, PassOwnPtr<ExecutionContextTask>, long long delayMs);
 
     bool m_started;
     bool m_terminated;
     bool m_shutdown;
     MessageQueue<WebThread::Task> m_debuggerMessageQueue;
     OwnPtr<WebThread::TaskObserver> m_microtaskRunner;
@@ skipping 16 matching lines @@
     // Used to signal thread shutdown.
     OwnPtr<WebWaitableEvent> m_shutdownEvent;
 
     // Used to signal thread termination.
     OwnPtr<WebWaitableEvent> m_terminationEvent;
 };
 
 } // namespace blink
 
 #endif // WorkerThread_h