Move blink scheduler implementation into a component

content/child/scheduler/nestable_single_thread_task_runner.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_NESTABLE_SINGLE_THREAD_TASK_RUNNER_H_
-#define CONTENT_CHILD_SCHEDULER_NESTABLE_SINGLE_THREAD_TASK_RUNNER_H_
-
-#include "base/single_thread_task_runner.h"
-#include "content/common/content_export.h"
-
-namespace content {
-
-// A single thread task runner which exposes whether it is running nested.
-class CONTENT_EXPORT NestableSingleThreadTaskRunner
-    : public base::SingleThreadTaskRunner {
- public:
-  NestableSingleThreadTaskRunner() {}
-
-  // Returns true if the task runner is nested (i.e., running a run loop within
-  // a nested task).
-  virtual bool IsNested() const = 0;
-
- protected:
-  ~NestableSingleThreadTaskRunner() override {}
-
-  DISALLOW_COPY_AND_ASSIGN(NestableSingleThreadTaskRunner);
-};
-
-}  // namespace content
-
-#endif  // CONTENT_CHILD_SCHEDULER_NESTABLE_SINGLE_THREAD_TASK_RUNNER_H_