TaskScheduler: Replace the SchedulerServiceThread with a base::Thread.

base/task_scheduler/delayed_task_manager.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_DELAYED_TASK_MANAGER_H_
-#define BASE_TASK_SCHEDULER_DELAYED_TASK_MANAGER_H_
-
-#include <stdint.h>
-
-#include <memory>
-#include <queue>
-#include <vector>
-
-#include "base/base_export.h"
-#include "base/callback.h"
-#include "base/macros.h"
-#include "base/memory/ref_counted.h"
-#include "base/task_scheduler/scheduler_lock.h"
-#include "base/task_scheduler/sequence.h"
-#include "base/task_scheduler/task.h"
-#include "base/time/time.h"
-
-namespace base {
-namespace internal {
-
-class SchedulerWorker;
-class SchedulerWorkerPool;
-
-// A DelayedTaskManager holds delayed Tasks until they become ripe for
-// execution. This class is thread-safe.
-class BASE_EXPORT DelayedTaskManager {
- public:
-  // |on_delayed_run_time_updated| is invoked when the delayed run time is
-  // updated as a result of adding a delayed task to the manager.
-  explicit DelayedTaskManager(const Closure& on_delayed_run_time_updated);
-  ~DelayedTaskManager();
-
-  // Adds |task| to a queue of delayed tasks. The task will be posted to
-  // |worker_pool| with |sequence| and |worker| the first time that
-  // PostReadyTasks() is called while Now() is passed |task->delayed_run_time|.
-  // |worker| is a SchedulerWorker owned by |worker_pool| or nullptr.
-  //
-  // TODO(robliao): Find a concrete way to manage the memory of |worker| and
-  // |worker_pool|. These objects are never deleted in production, but it is
-  // better not to spread this assumption throughout the scheduler.
-  void AddDelayedTask(std::unique_ptr<Task> task,
-                      scoped_refptr<Sequence> sequence,
-                      SchedulerWorker* worker,
-                      SchedulerWorkerPool* worker_pool);
-
-  // Posts delayed tasks that are ripe for execution.
-  void PostReadyTasks();
-
-  // Returns the next time at which a delayed task will become ripe for
-  // execution, or a null TimeTicks if there are no pending delayed tasks.
-  TimeTicks GetDelayedRunTime() const;
-
-  // Returns the current time. Can be overridden for tests.
-  virtual TimeTicks Now() const;
-
- private:
-  struct DelayedTask;
-  struct DelayedTaskComparator {
-    bool operator()(const DelayedTask& left, const DelayedTask& right) const;
-  };
-
-  const Closure on_delayed_run_time_updated_;
-
-  // Synchronizes access to all members below.
-  mutable SchedulerLock lock_;
-
-  // Priority queue of delayed tasks. The delayed task with the smallest
-  // |task->delayed_run_time| is in front of the priority queue.
-  using DelayedTaskQueue = std::priority_queue<DelayedTask,
-                                               std::vector<DelayedTask>,
-                                               DelayedTaskComparator>;
-  DelayedTaskQueue delayed_tasks_;
-
-  // The index to assign to the next delayed task added to the manager.
-  uint64_t delayed_task_index_ = 0;
-
-  DISALLOW_COPY_AND_ASSIGN(DelayedTaskManager);
-};
-
-}  // namespace internal
-}  // namespace base
-
-#endif  // BASE_TASK_SCHEDULER_DELAYED_TASK_MANAGER_H_