Ensures that audio tasks cannot run after AudioManager is deleted.

media/audio/cras/audio_manager_cras.h

Index: media/audio/cras/audio_manager_cras.h
diff --git a/media/audio/cras/audio_manager_cras.h b/media/audio/cras/audio_manager_cras.h
index e5a4b5b9e04a9c8e960f1d52451d6db1e5e792fe..fbe7097f8c091ee47ade455097a6e95d054c0b36 100644
--- a/media/audio/cras/audio_manager_cras.h
+++ b/media/audio/cras/audio_manager_cras.h
@@ -22,6 +22,7 @@ class MEDIA_EXPORT AudioManagerCras : public AudioManagerBase {
       scoped_refptr<base::SingleThreadTaskRunner> task_runner,
       scoped_refptr<base::SingleThreadTaskRunner> worker_task_runner,
       AudioLogFactory* audio_log_factory);
+  ~AudioManagerCras() override;
 
   // AudioManager implementation.
   bool HasAudioOutputDevices() override;
@@ -57,8 +58,6 @@ class MEDIA_EXPORT AudioManagerCras : public AudioManagerBase {
   bool IsDefault(const std::string& device_id, bool is_input);
 
  protected:
-  ~AudioManagerCras() override;
-
   AudioParameters GetPreferredOutputStreamParameters(
       const std::string& output_device_id,
       const AudioParameters& input_params) override;