Introduce a SchedulerHelper in content/child/scheduler

content/renderer/scheduler/renderer_scheduler_message_loop_delegate.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_RENDERER_SCHEDULER_RENDERER_SCHEDULER_MESSAGE_LOOP_DELEGATE_H_
-#define CONTENT_RENDERER_SCHEDULER_RENDERER_SCHEDULER_MESSAGE_LOOP_DELEGATE_H_
-
-#include "base/message_loop/message_loop.h"
-#include "content/common/content_export.h"
-#include "content/renderer/scheduler/nestable_single_thread_task_runner.h"
-
-namespace content {
-
-class CONTENT_EXPORT RendererSchedulerMessageLoopDelegate
-    : public NestableSingleThreadTaskRunner {
- public:
-  // |message_loop| is not owned and must outlive the lifetime of this object.
-  static scoped_refptr<RendererSchedulerMessageLoopDelegate> Create(
-      base::MessageLoop* message_loop);
-
-  // NestableSingleThreadTaskRunner implementation
-  bool PostDelayedTask(const tracked_objects::Location& from_here,
-                       const base::Closure& task,
-                       base::TimeDelta delay) override;
-  bool PostNonNestableDelayedTask(const tracked_objects::Location& from_here,
-                                  const base::Closure& task,
-                                  base::TimeDelta delay) override;
-  bool RunsTasksOnCurrentThread() const override;
-  bool IsNested() const override;
-
- protected:
-  ~RendererSchedulerMessageLoopDelegate() override;
-
- private:
-  RendererSchedulerMessageLoopDelegate(base::MessageLoop* message_loop);
-
-  // Not owned.
-  base::MessageLoop* message_loop_;
-
-  DISALLOW_COPY_AND_ASSIGN(RendererSchedulerMessageLoopDelegate);
-};
-
-}  // namespace content
-
-#endif  // CONTENT_RENDERER_SCHEDULER_RENDERER_SCHEDULER_MESSAGE_LOOP_DELEGATE_H_