Ensures that audio tasks cannot run after AudioManager is deleted.

media/audio/audio_manager_base.h

Index: media/audio/audio_manager_base.h
diff --git a/media/audio/audio_manager_base.h b/media/audio/audio_manager_base.h
index a80f63c1aef6b8b5150aadb7a7b077907f37bf4c..ec9322319a11118a109a81781d665388301497d0 100644
--- a/media/audio/audio_manager_base.h
+++ b/media/audio/audio_manager_base.h
@@ -111,16 +111,11 @@ class MEDIA_EXPORT AudioManagerBase : public AudioManager {
   int output_stream_count() const { return num_output_streams_; }
 
  protected:
-  AudioManagerBase(
-      scoped_refptr<base::SingleThreadTaskRunner> task_runner,
-      scoped_refptr<base::SingleThreadTaskRunner> worker_task_runner,
-      AudioLogFactory* audio_log_factory);
-
-  // Releases all the audio output dispatchers.
-  // All audio streams should be closed before Shutdown() is called.
-  // This must be called in the destructor of every AudioManagerBase
-  // implementation.
-  void Shutdown();
+  AudioManagerBase(std::unique_ptr<AudioThread> audio_thread,
+                   AudioLogFactory* audio_log_factory);
+
+  // AudioManager:
+  void ShutdownOnAudioThread() override;
 
   void SetMaxOutputStreamsAllowed(int max) { max_num_output_streams_ = max; }