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_