Ensures that audio tasks cannot run after AudioManager is deleted.

media/audio/pulse/audio_manager_pulse.cc

Index: media/audio/pulse/audio_manager_pulse.cc
diff --git a/media/audio/pulse/audio_manager_pulse.cc b/media/audio/pulse/audio_manager_pulse.cc
index 779bf92e58d3d39c981f398cf911ed504bc2191f..ff27837e768dd6ff74153e01fe11c7f0e1cc44a2 100644
--- a/media/audio/pulse/audio_manager_pulse.cc
+++ b/media/audio/pulse/audio_manager_pulse.cc
@@ -63,12 +63,7 @@ AudioManagerPulse::AudioManagerPulse(
   SetMaxOutputStreamsAllowed(kMaxOutputStreams);
 }
 
-AudioManagerPulse::~AudioManagerPulse() {
-  Shutdown();
-  // The Pulse objects are the last things to be destroyed since Shutdown()
-  // needs them.
-  DestroyPulse();
-}
+AudioManagerPulse::~AudioManagerPulse() = default;
 
 bool AudioManagerPulse::Init() {
   // TODO(alokp): Investigate if InitPulse can happen on the audio thread.
@@ -79,7 +74,13 @@ bool AudioManagerPulse::Init() {
   return InitPulse();
 }
 
-// Implementation of AudioManager.
+void AudioManagerPulse::Shutdown() {
+  AudioManagerBase::Shutdown();
+  // The Pulse objects are the last things to be destroyed since Shutdown()
+  // needs them.
+  DestroyPulse();
+}
+
 bool AudioManagerPulse::HasAudioOutputDevices() {
   AudioDeviceNames devices;
   GetAudioOutputDeviceNames(&devices);