TaskScheduler: Delegate instead of callbacks for SchedulerWorkerThread.

base/task_scheduler/scheduler_worker_thread_delegate.h

+// Copyright 2016 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 BASE_TASK_SCHEDULER_SCHEDULER_WORKER_THREAD_DELEGATE_H_
+#define BASE_TASK_SCHEDULER_SCHEDULER_WORKER_THREAD_DELEGATE_H_
+
+#include "base/memory/ref_counted.h"
+#include "base/task_scheduler/sequence.h"
+
+namespace base {
+namespace internal {
+
+// Delegate interface for SchedulerWorkerThread. The methods are always called
+// from the thread managed by the SchedulerWorkerThread instance.
+class SchedulerWorkerThreadDelegate {
+ public:
+  // Called when the main function of the SchedulerWorkerThread is entered.

[robliao, 2016/04/06 21:28:20]

Nit: 'SchedulerWorkerThread starts.'

'SchedulerWorkerThread enters' works too.

[fdoray, 2016/04/07 13:53:41]

Done.

+  virtual void OnMainEntry() = 0;
+
+  // Called when the main function of the SchedulerWorkerThread exits.
+  virtual void OnMainExit() = 0;
+
+  // Called by the SchedulerWorkerThread to get a Sequence from which to run a
+  // Task.
+  virtual scoped_refptr<Sequence> GetWork() = 0;
+
+  // Called after the SchedulerWorkerThread has tried to run a Task from
+  // |sequence| (a TaskTracker might have prevented the Task from running).
+  virtual void RanTaskFromSequence(scoped_refptr<Sequence> sequence) = 0;
+};
+
+}  // namespace internal
+}  // namespace base
+
+#endif  // BASE_TASK_SCHEDULER_SCHEDULER_WORKER_THREAD_DELEGATE_H_