Introduce a SchedulerHelper in content/child/scheduler

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_RENDERER_SCHEDULER_NESTABLE_SINGLE_THREAD_TASK_RUNNER_H_
-#define CONTENT_RENDERER_SCHEDULER_NESTABLE_SINGLE_THREAD_TASK_RUNNER_H_
+#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_RENDERER_SCHEDULER_NESTABLE_SINGLE_THREAD_TASK_RUNNER_H_
+#endif  // CONTENT_CHILD_SCHEDULER_NESTABLE_SINGLE_THREAD_TASK_RUNNER_H_