Ensures that audio tasks cannot run after AudioManager is deleted.

media/audio/alsa/audio_manager_alsa.cc

Index: media/audio/alsa/audio_manager_alsa.cc
diff --git a/media/audio/alsa/audio_manager_alsa.cc b/media/audio/alsa/audio_manager_alsa.cc
index 72c48e3327a88062e87938819bb471d82ff7e6cd..33fc0b2ddb918120e8c4bd49de8dde537340b7bb 100644
--- a/media/audio/alsa/audio_manager_alsa.cc
+++ b/media/audio/alsa/audio_manager_alsa.cc
@@ -78,7 +78,15 @@ void AudioManagerAlsa::ShowLinuxAudioInputSettings() {
   base::LaunchProcess(command_line, base::LaunchOptions());
 }
 
-// Implementation of AudioManager.
+AudioManagerAlsa::AudioManagerAlsa(std::unique_ptr<AudioThread> audio_thread,
+                                   AudioLogFactory* audio_log_factory)
+    : AudioManagerBase(std::move(audio_thread), audio_log_factory),
+      wrapper_(new AlsaWrapper()) {
+  SetMaxOutputStreamsAllowed(kMaxOutputStreams);
+}
+
+AudioManagerAlsa::~AudioManagerAlsa() = default;
+
 bool AudioManagerAlsa::HasAudioOutputDevices() {
   return HasAnyAlsaAudioDevice(kStreamPlayback);
 }
@@ -87,21 +95,6 @@ bool AudioManagerAlsa::HasAudioInputDevices() {
   return HasAnyAlsaAudioDevice(kStreamCapture);
 }
 
-AudioManagerAlsa::AudioManagerAlsa(
-    scoped_refptr<base::SingleThreadTaskRunner> task_runner,
-    scoped_refptr<base::SingleThreadTaskRunner> worker_task_runner,
-    AudioLogFactory* audio_log_factory)
-    : AudioManagerBase(std::move(task_runner),
-                       std::move(worker_task_runner),
-                       audio_log_factory),
-      wrapper_(new AlsaWrapper()) {
-  SetMaxOutputStreamsAllowed(kMaxOutputStreams);
-}
-
-AudioManagerAlsa::~AudioManagerAlsa() {
-  Shutdown();
-}
-
 void AudioManagerAlsa::ShowAudioInputSettings() {
   ShowLinuxAudioInputSettings();
 }