Create base::test::ScopedTaskScheduler.

base/test/scoped_task_scheduler.cc

+// 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.
+
+#include "base/test/scoped_task_scheduler.h"
+
+#include <vector>
+
+#include "base/bind.h"
+#include "base/task_scheduler/scheduler_worker_pool_params.h"
+#include "base/task_scheduler/task_scheduler.h"
+#include "base/threading/platform_thread.h"
+#include "base/time/time.h"
+
+namespace base {
+namespace test {
+
+namespace {
+
+size_t GetWorkerPoolIndexForTraits(const TaskTraits&) {
+  // All TaskTraits are mapped to the single worker pool.
+  return 0;
+}
+
+}  // namespace
+
+ScopedTaskScheduler::ScopedTaskScheduler() {
+  DCHECK(!TaskScheduler::GetInstance());
+
+  // Create a TaskScheduler with a single thread to make tests deterministic.
+  std::vector<SchedulerWorkerPoolParams> worker_pool_params_vector;
+  worker_pool_params_vector.emplace_back(
+      "Test", ThreadPriority::NORMAL,
+      SchedulerWorkerPoolParams::IORestriction::ALLOWED, 1, TimeDelta::Max());
+  TaskScheduler::CreateAndSetDefaultTaskScheduler(
+      worker_pool_params_vector, Bind(&GetWorkerPoolIndexForTraits));
+}
+
+ScopedTaskScheduler::~ScopedTaskScheduler() {
+  DCHECK(TaskScheduler::GetInstance());

[robliao, 2016/11/16 21:23:05]

Maybe we can keep a pointer and check the pointer is still equal to
TaskScheduler::GetInstance() to guard against folks who may initialize a task
scheduler down the line without checking GetInstance().

[fdoray, 2016/11/16 22:04:45]

Done.

+  TaskScheduler::GetInstance()->Shutdown();
+  TaskScheduler::GetInstance()->JoinForTesting();
+  TaskScheduler::SetInstance(nullptr);
+}
+
+}  // namespace test
+}  // namespace base