Worker: Introduce an observation mechanism for WorkerThread termination

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 14 matching lines @@
  */
 
 #ifndef WorkerThread_h
 #define WorkerThread_h
 
 #include "core/CoreExport.h"
 #include "core/dom/ExecutionContextTask.h"
 #include "core/frame/csp/ContentSecurityPolicy.h"
 #include "core/workers/WorkerGlobalScope.h"
 #include "core/workers/WorkerLoaderProxy.h"
+#include "core/workers/WorkerThreadLifecycleObserver.h"
+#include "platform/LifecycleNotifier.h"
 #include "wtf/Forward.h"
 #include "wtf/Functional.h"
 #include "wtf/OwnPtr.h"
 #include "wtf/PassRefPtr.h"
 #include <v8.h>
 
 namespace blink {
 
 class InspectorTaskRunner;
 class WaitableEvent;
 class WorkerBackingThread;
 class WorkerGlobalScope;
 class WorkerInspectorController;
 class WorkerReportingProxy;
 class WorkerThreadStartupData;
 
 enum WorkerThreadStartMode {
     DontPauseWorkerGlobalScopeOnStart,
     PauseWorkerGlobalScopeOnStart
 };
 
+// Used for notifying observers on the main thread of worker thread termination.
+// The lifetime of this class is equal to that of WorkerThread. Created and
+// destructed on the main thread.
+class CORE_EXPORT WorkerThreadContext final : public GarbageCollectedFinalized<WorkerThreadContext>, public LifecycleNotifier<WorkerThreadContext, WorkerThreadLifecycleObserver> {

[kinuko, 2016/06/10 02:05:28]

nit: This very generic, yet another -context class which doesn't do much
concerns me a bit.  Could this be given more specific, descriptive name? Maybe-
WorkerThreadLifecycleContext or WorkerLifecycleContext?

+    USING_GARBAGE_COLLECTED_MIXIN(WorkerThreadContext);
+    WTF_MAKE_NONCOPYABLE(WorkerThreadContext);
+public:
+    WorkerThreadContext();
+    ~WorkerThreadContext() override;
+    void notifyContextDestroyed() override;
+
+private:
+    friend class WorkerThreadLifecycleObserver;
+    bool m_wasContextDestroyed = false;
+};
+
 // WorkerThread is a kind of WorkerBackingThread client. Each worker mechanism
 // can access the lower thread infrastructure via an implementation of this
 // abstract class. Multiple WorkerThreads can share one WorkerBackingThread.
 // See WorkerBackingThread.h for more details.
 //
 // WorkerThread start and termination must be initiated on the main thread and
 // an actual task is executed on the worker thread.
 //
 // When termination starts, (debugger) tasks on WorkerThread are handled as
 // follows:
@@ skipping 47 matching lines @@
     void appendDebuggerTask(std::unique_ptr<CrossThreadClosure>);
 
     // Runs only debugger tasks while paused in debugger.
     void startRunningDebuggerTasksOnPauseOnWorkerThread();
     void stopRunningDebuggerTasksOnPauseOnWorkerThread();
 
     // Can be called only on the worker thread, WorkerGlobalScope is not thread
     // safe.
     WorkerGlobalScope* workerGlobalScope();
 
+    // Called for creating WorkerThreadLifecycleObserver on both the main thread
+    // and the worker thread.
+    WorkerThreadContext* workerThreadContext() const { return m_workerThreadContext; }

[kinuko, 2016/06/10 02:05:28]

nit: I know this file is consistently in the old style, but workerThreadContext
should be getWorkerThreadContext

+
     // Returns true once one of the terminate* methods is called.
     bool terminated();
 
     // Number of active worker threads.
     static unsigned workerThreadCount();
 
     PlatformThreadId platformThreadId();
 
     ExitCode getExitCode();
 
@@ skipping 63 matching lines @@
 
     // Signaled when the thread starts termination on the main thread.
     OwnPtr<WaitableEvent> m_terminationEvent;
 
     // Signaled when the thread completes termination on the worker thread.
     OwnPtr<WaitableEvent> m_shutdownEvent;
 
     // Scheduled when termination starts with TerminationMode::Force, and
     // cancelled when the worker thread is gracefully shut down.
     OwnPtr<ForceTerminationTask> m_scheduledForceTerminationTask;
+
+    Persistent<WorkerThreadContext> m_workerThreadContext;
 };
 
 } // namespace blink
 
 #endif // WorkerThread_h