Ensures that audio tasks cannot run after AudioManager is deleted.

media/audio/audio_thread_impl.h

Index: media/audio/audio_thread_impl.h
diff --git a/media/audio/audio_thread_impl.h b/media/audio/audio_thread_impl.h
new file mode 100644
index 0000000000000000000000000000000000000000..89a40df1a073948cb3edd69459273afe78381d20
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+++ b/media/audio/audio_thread_impl.h
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+// 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 MEDIA_AUDIO_AUDIO_THREAD_IMPL_H_
+#define MEDIA_AUDIO_AUDIO_THREAD_IMPL_H_
+
+#include "base/threading/thread.h"
+#include "base/threading/thread_checker.h"
+#include "media/audio/audio_thread.h"
+
+namespace media {
+
+class MEDIA_EXPORT AudioThreadImpl : public AudioThread {
+ public:
+  AudioThreadImpl();
+  ~AudioThreadImpl() override;
+
+  // AudioThread implementation.
+  void Stop() override;
+  base::SingleThreadTaskRunner* GetTaskRunner() override;
+  base::SingleThreadTaskRunner* GetWorkerTaskRunner() override;
+
+ private:
+  base::Thread thread_;
+  scoped_refptr<base::SingleThreadTaskRunner> task_runner_;
+  scoped_refptr<base::SingleThreadTaskRunner> worker_task_runner_;
+
+  THREAD_CHECKER(thread_checker_);
+  DISALLOW_COPY_AND_ASSIGN(AudioThreadImpl);
+};
+
+}  // namespace content
+
+#endif  // MEDIA_AUDIO_AUDIO_THREAD_IMPL_H_