Pass task runners to AudioManager constructor.

media/audio/android/audio_manager_android.cc

Index: media/audio/android/audio_manager_android.cc
diff --git a/media/audio/android/audio_manager_android.cc b/media/audio/android/audio_manager_android.cc
index 96a7c78c29c055d099f5ee985a8a591bfe44c3a8..4563a0aecf26288624674f61ca6c5da11113ebe8 100644
--- a/media/audio/android/audio_manager_android.cc
+++ b/media/audio/android/audio_manager_android.cc
@@ -45,12 +45,22 @@ const int kDefaultOutputBufferSize = 2048;
 
 }  // namespace
 
-AudioManager* CreateAudioManager(AudioLogFactory* audio_log_factory) {
-  return new AudioManagerAndroid(audio_log_factory);
-}
-
-AudioManagerAndroid::AudioManagerAndroid(AudioLogFactory* audio_log_factory)
-    : AudioManagerBase(audio_log_factory),
+ScopedAudioManagerPtr CreateAudioManager(
+    scoped_refptr<base::SingleThreadTaskRunner> task_runner,
+    scoped_refptr<base::SingleThreadTaskRunner> worker_task_runner,
+    AudioLogFactory* audio_log_factory) {
+  return ScopedAudioManagerPtr(new AudioManagerAndroid(
+      std::move(task_runner), std::move(worker_task_runner),
+      audio_log_factory));
+}
+
+AudioManagerAndroid::AudioManagerAndroid(
+    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),
       communication_mode_is_on_(false),
       output_volume_override_set_(false),
       output_volume_override_(0) {
@@ -68,11 +78,11 @@ AudioManagerAndroid::AudioManagerAndroid(AudioLogFactory* audio_log_factory)
 }
 
 AudioManagerAndroid::~AudioManagerAndroid() {
-  // It's safe to post a task here since Shutdown() will wait for all tasks to
-  // complete before returning.
-  GetTaskRunner()->PostTask(FROM_HERE, base::Bind(
-      &AudioManagerAndroid::ShutdownOnAudioThread, base::Unretained(this)));
-  Shutdown();
+  DCHECK(GetTaskRunner()->BelongsToCurrentThread());

[DaleCurtis, 2016/04/06 22:07:49]

Hmm, this might be a bit dicy in the future since j_audio_manager_ is used by
ReleaseInputStream(), but I suppose at this point there should be zero input
streams which is okay for now.

[alokp, 2016/04/07 00:38:10]

We have a DCHECK_EQ(0, num_input_streams_) in AudioManagerBase destructor, which
should catch this, although I agree it does look dicy. If this is a problem, we
will need to post a task to destroy j_audio_manager_ similar to what we are
doing in Pulse.

[tommi (sloooow) - chröme, 2016/04/07 14:33:40]

What do you think about upgrading that to CHECK_EQ?  I'd like to do that for all
platforms actually, so if we're confident with this requirement being met, maybe
we should do that.  I think it's an important enough design assertion and if we
don't meet it, there's a chance of a use-after-free.

[DaleCurtis, 2016/04/07 17:23:09]

+1 I think we should do this, though it'll be hard to be actionable given the
amount of information available at time of destruction. It won't catch all
problem cases either. The risk case is: previously the thread stopped during
destruction w/ a join, now it will stop after destruction. If anything during
destruction posts another task to the task runner thread doing things with an
audio manager we'll have problems.

+  DVLOG(2) << "Destroying Java part of the audio manager";
+  Java_AudioManagerAndroid_close(base::android::AttachCurrentThread(),
+                                 j_audio_manager_.obj());
+  j_audio_manager_.Reset();
 }
 
 bool AudioManagerAndroid::HasAudioOutputDevices() {
@@ -337,15 +347,6 @@ void AudioManagerAndroid::InitializeOnAudioThread() {
       j_audio_manager_.obj());
 }
 
-void AudioManagerAndroid::ShutdownOnAudioThread() {
-  DCHECK(GetTaskRunner()->BelongsToCurrentThread());
-  DVLOG(2) << "Destroying Java part of the audio manager";
-  Java_AudioManagerAndroid_close(
-      base::android::AttachCurrentThread(),
-      j_audio_manager_.obj());
-  j_audio_manager_.Reset();
-}
-
 void AudioManagerAndroid::SetCommunicationAudioModeOn(bool on) {
   Java_AudioManagerAndroid_setCommunicationAudioModeOn(
       base::android::AttachCurrentThread(),