Adds a flag to support "Virtual Time" to the blink scheduler

components/scheduler/child/scheduler_task_runner_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 COMPONENTS_SCHEDULER_CHILD_SCHEDULER_TASK_RUNNER_DELEGATE_H_
-#define COMPONENTS_SCHEDULER_CHILD_SCHEDULER_TASK_RUNNER_DELEGATE_H_
-
-#include "base/message_loop/message_loop.h"
-#include "components/scheduler/base/nestable_single_thread_task_runner.h"
-#include "components/scheduler/scheduler_export.h"
-
-namespace scheduler {
-
-class SCHEDULER_EXPORT SchedulerTaskRunnerDelegate
-    : public NestableSingleThreadTaskRunner {
- public:
-  SchedulerTaskRunnerDelegate() {}
-
-  // If the underlying task runner supports the concept of a default task
-  // runner, the delegate should implement this function to redirect that task
-  // runner to the scheduler.
-  virtual void SetDefaultTaskRunner(
-      scoped_refptr<base::SingleThreadTaskRunner> task_runner) = 0;
-
-  // Similarly this method can be used to restore the original task runner when
-  // the scheduler no longer wants to intercept tasks.
-  virtual void RestoreDefaultTaskRunner() = 0;
-
- protected:
-  ~SchedulerTaskRunnerDelegate() override {}
-
-  DISALLOW_COPY_AND_ASSIGN(SchedulerTaskRunnerDelegate);
-};
-
-}  // namespace scheduler
-
-#endif  // COMPONENTS_SCHEDULER_CHILD_SCHEDULER_TASK_RUNNER_DELEGATE_H_