Ensures that audio tasks cannot run after AudioManager is deleted.

chromecast/media/audio/cast_audio_manager.cc

 // Copyright 2015 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.
 
 #include "chromecast/media/audio/cast_audio_manager.h"
 
 #include <algorithm>
 #include <string>
 
 #include "base/bind.h"
@@ skipping 34 matching lines @@
     scoped_refptr<base::SingleThreadTaskRunner> worker_task_runner,
     ::media::AudioLogFactory* audio_log_factory,
     MediaPipelineBackendManager* backend_manager,
     CastAudioMixer* audio_mixer)
     : AudioManagerBase(std::move(task_runner),
                        std::move(worker_task_runner),
                        audio_log_factory),
       backend_manager_(backend_manager),
       mixer_(audio_mixer) {}
 
-CastAudioManager::~CastAudioManager() {
-  Shutdown();
-}
+CastAudioManager::~CastAudioManager() = default;
 
 bool CastAudioManager::HasAudioOutputDevices() {
   return true;
 }
 
 bool CastAudioManager::HasAudioInputDevices() {
   return false;
 }
 
 void CastAudioManager::ShowAudioInputSettings() {
@@ skipping 111 matching lines @@
   DCHECK(!mixer_output_stream_);  // Only allow 1 |mixer_output_stream_|.
 
   // Keep a reference to this stream for proper behavior on
   // CastAudioManager::ReleaseOutputStream.
   mixer_output_stream_.reset(new CastAudioOutputStream(params, this));
   return mixer_output_stream_.get();
 }
 
 }  // namespace media
 }  // namespace chromecast