Worker: Introduce per-global-scope task scheduler

third_party/WebKit/Source/platform/scheduler/child/webthread_impl_for_worker_scheduler.h

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef THIRD_PARTY_WEBKIT_PUBLIC_PLATFORM_SCHEDULER_CHILD_WEBTHREAD_IMPL_FOR_WORKER_SCHEDULER_H_
 #define THIRD_PARTY_WEBKIT_PUBLIC_PLATFORM_SCHEDULER_CHILD_WEBTHREAD_IMPL_FOR_WORKER_SCHEDULER_H_
 
 #include "base/threading/thread.h"
 #include "public/platform/WebPrivatePtr.h"
 #include "public/platform/scheduler/child/webthread_base.h"
@@ skipping 30 matching lines @@
   WebTaskRunner* GetWebTaskRunner() override;
 
   // WebThreadBase implementation.
   base::SingleThreadTaskRunner* GetTaskRunner() const override;
   scheduler::SingleThreadIdleTaskRunner* GetIdleTaskRunner() const override;
   void Init() override;
 
   // base::MessageLoop::DestructionObserver implementation.
   void WillDestroyCurrentMessageLoop() override;
 
+  scheduler::WorkerScheduler* GetWorkerScheduler() {
+    return worker_scheduler_.get();

[haraken, 2017/04/13 07:03:36]

It looks strange that:

- webthread_impl_for_worker_scheduler owns the scheduler by std::unique_ptr.

- the caller site also owns the scheduler by creating another std::unique_ptr by
calling MakeUnique(GetWorkerScheduler()).

Who should own the scheduler?

[nhiroki, 2017/04/13 08:23:50]

That MakeUnique creates Worker*GlobalScope*Scheduler, and it does NOT own the
passed WorkerScheduler.
- WebThreadImplForWorkerScheduler owns WorkerScheduler
    (per-thread object owns per-thread scheduler).
- WorkerThread owns WorkerGlobalScopeScheduler
    (per-global-scope object the per-global-scope scheduler)

+  }
+
  protected:
   base::Thread* GetThread() const { return thread_.get(); }
+  SchedulerTqmDelegate* task_runner_delegate() const {
+    return task_runner_delegate_.get();
+  }
 
  private:
   virtual std::unique_ptr<scheduler::WorkerScheduler> CreateWorkerScheduler();
 
   void AddTaskObserverInternal(
       base::MessageLoop::TaskObserver* observer) override;
   void RemoveTaskObserverInternal(
       base::MessageLoop::TaskObserver* observer) override;
 
   void InitOnThread(base::WaitableEvent* completion);
   void RestoreTaskRunnerOnThread(base::WaitableEvent* completion);
 
   std::unique_ptr<base::Thread> thread_;
   std::unique_ptr<scheduler::WorkerScheduler> worker_scheduler_;
   std::unique_ptr<scheduler::WebSchedulerImpl> web_scheduler_;
   scoped_refptr<base::SingleThreadTaskRunner> thread_task_runner_;
   scoped_refptr<TaskQueue> task_runner_;
   scoped_refptr<scheduler::SingleThreadIdleTaskRunner> idle_task_runner_;
   scoped_refptr<SchedulerTqmDelegate> task_runner_delegate_;
   WebPrivatePtr<WebTaskRunnerImpl> web_task_runner_;
 };
 
 }  // namespace scheduler
 }  // namespace blink
 
 #endif  // THIRD_PARTY_WEBKIT_PUBLIC_PLATFORM_SCHEDULER_CHILD_WEBTHREAD_IMPL_FOR_WORKER_SCHEDULER_H_