Ensures that audio tasks cannot run after AudioManager is deleted.

media/audio/mock_audio_manager.h

Index: media/audio/mock_audio_manager.h
diff --git a/media/audio/mock_audio_manager.h b/media/audio/mock_audio_manager.h
index 781729a56ca02f7c4b32d33d16b9a1f5fb97a6f8..9dd5cb8548651f73c6a6a7e9b6daee0626542bc1 100644
--- a/media/audio/mock_audio_manager.h
+++ b/media/audio/mock_audio_manager.h
@@ -18,19 +18,15 @@ namespace media {
 // would causing failures on classes which expect that.
 class MockAudioManager : public AudioManager {
  public:
-  class Deleter {
-   public:
-    void operator()(const MockAudioManager* instance) const;
-  };
-
-  using UniquePtr = std::unique_ptr<MockAudioManager, Deleter>;
   using GetDeviceDescriptionsCallback =
       base::RepeatingCallback<void(AudioDeviceDescriptions*)>;
   using GetAssociatedOutputDeviceIDCallback =
       base::RepeatingCallback<std::string(const std::string&)>;
 
-  explicit MockAudioManager(
-      scoped_refptr<base::SingleThreadTaskRunner> task_runner);
+  explicit MockAudioManager(std::unique_ptr<AudioThread> audio_thread);
+  ~MockAudioManager() override;
+
+  void ShutdownOnAudioThread() override;
 
   bool HasAudioOutputDevices() override;
 
@@ -95,12 +91,7 @@ class MockAudioManager : public AudioManager {
   void SetAssociatedOutputDeviceIDCallback(
       GetAssociatedOutputDeviceIDCallback callback);
 
- protected:
-  ~MockAudioManager() override;
-
  private:
-  friend class base::DeleteHelper<MockAudioManager>;
-
   AudioParameters input_params_;
   AudioParameters output_params_;
   AudioParameters default_output_params_;