Task Scheduler.

base/task_scheduler/task_scheduler.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_TASK_SCHEDULER_H_
+#define BASE_TASK_SCHEDULER_TASK_SCHEDULER_H_
+
+#include "base/base_export.h"
+#include "base/callback_forward.h"
+#include "base/macros.h"
+#include "base/memory/ref_counted.h"
+#include "base/memory/scoped_ptr.h"
+#include "base/task_runner.h"
+#include "base/task_scheduler/task_traits.h"
+
+namespace tracked_objects {
+class Location;
+}
+
+namespace base {
+
+class BASE_EXPORT TaskScheduler {
+ public:
+  // Posts |task| with specific |traits|.
+  // For one off tasks that don't require a TaskRunner.
+  virtual void PostTaskWithTraits(const tracked_objects::Location& from_here,
+                                  TaskTraits traits,
+                                  const Closure& task) = 0;
+
+  // Returns a TaskRunner whose PostTask invocations will result in scheduling
+  // tasks using |traits| which will be executed according to |execution_mode|.
+  virtual scoped_refptr<TaskRunner> CreateTaskRunnerWithTraits(
+      TaskTraits traits,
+      ExecutionMode execution_mode) = 0;
+
+  // Performs a synchronous cleanup of threads and state in the TaskScheduler.
+  virtual void Shutdown() = 0;
+
+  // Registers |task_scheduler| to handle tasks posted through the post_task.h
+  // API for this process. Must be called on the main thread before creating any
+  // other threads. Replacing an existing TaskScheduler is not supported (this
+  // may not be called after InitializeDefaultTaskScheduler() or SetInstance()
+  // was already called in this process).
+  static void SetInstance(scoped_ptr<TaskScheduler> task_scheduler);
+
+  // Retrieve the TaskScheduler set via SetInstance(). This should be used very
+  // rarely; most users of TaskScheduler should use the post_task.h API.
+  static TaskScheduler* GetInstance();
+
+  // Initializes the default task scheduler for this process. Must be called on
+  // the main thread before creating any other threads. Replacing an existing
+  // TaskScheduler is not supported (this may not be called after
+  // InitializeDefaultTaskScheduler() or SetInstance() was already called in
+  // this process).
+  static void InitializeDefaultTaskScheduler();
+
+  virtual ~TaskScheduler() = default;
+};
+
+}  // namespace base
+
+#endif  // BASE_TASK_SCHEDULER_TASK_SCHEDULER_H_