Ensures that audio tasks cannot run after AudioManager is deleted.

content/browser/audio_manager_thread.h

-// Copyright 2016 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_BROWSER_AUDIO_MANAGER_THREAD_H_
-#define CONTENT_BROWSER_AUDIO_MANAGER_THREAD_H_
-
-#include "base/memory/ref_counted.h"
-#include "base/threading/thread.h"
-#include "content/common/content_export.h"
-
-namespace content {
-
-// This class encapulates the logic for the thread and task runners that the
-// AudioManager and related classes run on. audio_task_runner and
-// worker_task_runner should be called on the same thread as the
-// AudioManagerThread was constructed on.
-class CONTENT_EXPORT AudioManagerThread {
- public:
-  // Constructs and starts a thread. On all platforms except for Mac, the
-  // started thread becomes the audio task runner. However, on Mac, the task
-  // runner this object is constructed on will become the audio thread and the
-  // thread is only used for high complexity tasks which can't be run on the
-  // main thread (typically the UI thread).
-  AudioManagerThread();
-  ~AudioManagerThread();
-
-  scoped_refptr<base::SingleThreadTaskRunner> task_runner() const {
-    return task_runner_;
-  };
-
-  scoped_refptr<base::SingleThreadTaskRunner> worker_task_runner() const {
-    return thread_.task_runner();
-  }
-
- private:
-  base::Thread thread_;
-
-  // Task runner to run audio control calls on.
-  scoped_refptr<base::SingleThreadTaskRunner> task_runner_;
-
-  DISALLOW_COPY_AND_ASSIGN(AudioManagerThread);
-};
-
-}  // namespace content
-
-#endif  // CONTENT_BROWSER_AUDIO_MANAGER_THREAD_H_