Revert of Revert of Add a WorkerScheduler and a WebThreadImplForWorker

content/child/scheduler/null_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 CONTENT_CHILD_SCHEDULER_NULL_WORKER_SCHEDULER_H_
+#define CONTENT_CHILD_SCHEDULER_NULL_WORKER_SCHEDULER_H_
+
+#include "content/child/scheduler/worker_scheduler.h"
+
+namespace content {
+
+class NullWorkerScheduler : public WorkerScheduler {
+ public:
+  NullWorkerScheduler();
+  ~NullWorkerScheduler() override;
+
+  scoped_refptr<base::SingleThreadTaskRunner> DefaultTaskRunner() override;
+  scoped_refptr<SingleThreadIdleTaskRunner> IdleTaskRunner() override;
+
+  void AddTaskObserver(base::MessageLoop::TaskObserver* task_observer) override;
+  void RemoveTaskObserver(
+      base::MessageLoop::TaskObserver* task_observer) override;
+  bool CanExceedIdleDeadlineIfRequired() const override;
+  void Init() override;
+  void Shutdown() override;
+
+ private:
+  scoped_refptr<base::SingleThreadTaskRunner> task_runner_;
+  scoped_refptr<SingleThreadIdleTaskRunner> idle_task_runner_;
+
+  DISALLOW_COPY_AND_ASSIGN(NullWorkerScheduler);
+};
+
+}  // namespace content
+
+#endif  // CONTENT_CHILD_SCHEDULER_NULL_WORKER_SCHEDULER_H_