Tab Audio Capture: Browser-side connect/disconnect functionality.

media/audio/audio_output_controller.cc

Index: media/audio/audio_output_controller.cc
diff --git a/media/audio/audio_output_controller.cc b/media/audio/audio_output_controller.cc
index 50850c9265cdd2b0f503e97994a122b70167047d..1375c5d0d303b1028f833586ac6dff84b9b83c34 100644
--- a/media/audio/audio_output_controller.cc
+++ b/media/audio/audio_output_controller.cc
@@ -29,15 +29,19 @@ AudioOutputController::AudioOutputController(AudioManager* audio_manager,
                                              const AudioParameters& params,
                                              SyncReader* sync_reader)
     : audio_manager_(audio_manager),
+      params_(params),
       handler_(handler),
       stream_(NULL),
+      diverting_to_stream_(NULL),
       volume_(1.0),
       state_(kEmpty),
       sync_reader_(sync_reader),
       message_loop_(audio_manager->GetMessageLoop()),
       number_polling_attempts_left_(0),
-      params_(params),
       ALLOW_THIS_IN_INITIALIZER_LIST(weak_this_(this)) {
+  // This thread-checker is only used to ensure calls to StartDiverting() and
+  // StopDiverting() are made by the same single outside thread.
+  divert_thread_checker_.DetachFromThread();
 }
 
 AudioOutputController::~AudioOutputController() {
@@ -70,13 +74,10 @@ scoped_refptr<AudioOutputController> AudioOutputController::Create(
   if (!params.IsValid() || !audio_manager)
     return NULL;
 
-  // Starts the audio controller thread.
   scoped_refptr<AudioOutputController> controller(new AudioOutputController(
       audio_manager, event_handler, params, sync_reader));
-
   controller->message_loop_->PostTask(FROM_HERE, base::Bind(
       &AudioOutputController::DoCreate, controller));
-
   return controller;
 }
 
@@ -120,7 +121,8 @@ void AudioOutputController::DoCreate() {
   DCHECK(state_ == kEmpty || state_ == kRecreating) << state_;
 
   DoStopCloseAndClearStream(NULL);
-  stream_ = audio_manager_->MakeAudioOutputStreamProxy(params_);
+  stream_ = diverting_to_stream_ ? diverting_to_stream_ :
+      audio_manager_->MakeAudioOutputStreamProxy(params_);
   if (!stream_) {
     state_ = kError;
 
@@ -138,9 +140,11 @@ void AudioOutputController::DoCreate() {
     return;
   }
 
-  // Everything started okay, so register for state change callbacks if we have
-  // not already done so.
-  if (state_ != kRecreating)
+  // Everything started okay, so re-register for state change callbacks if
+  // stream_ was created via AudioManager.  Note: The call to
+  // DoStopCloseAndClearStream() above called
+  // RemoveOutputDeviceChangeListener().
+  if (stream_ != diverting_to_stream_)
     audio_manager_->AddOutputDeviceChangeListener(this);
 
   // We have successfully opened the stream. Set the initial volume.
@@ -348,13 +352,17 @@ void AudioOutputController::DoStopCloseAndClearStream(WaitableEvent* done) {
 
   // Allow calling unconditionally and bail if we don't have a stream_ to close.
   if (stream_) {
+    // De-register from state change callbacks if stream_ was created via
+    // AudioManager.
+    if (stream_ != diverting_to_stream_)
+      audio_manager_->RemoveOutputDeviceChangeListener(this);
+
     stream_->Stop();
     stream_->Close();
+    if (stream_ == diverting_to_stream_)
+      diverting_to_stream_ = NULL;
     stream_ = NULL;
 
-    audio_manager_->RemoveOutputDeviceChangeListener(this);
-    audio_manager_ = NULL;
-
     weak_this_.InvalidateWeakPtrs();
   }
 
@@ -366,16 +374,9 @@ void AudioOutputController::DoStopCloseAndClearStream(WaitableEvent* done) {
 void AudioOutputController::OnDeviceChange() {
   DCHECK(message_loop_->BelongsToCurrentThread());
 
-  // We should always have a stream by this point.
-  CHECK(stream_);
-
-  // Preserve the original state and shutdown the stream.
-  State original_state = state_;
-  stream_->Stop();
-  stream_->Close();
-  stream_ = NULL;
-
-  // Recreate the stream, exit if we ran into an error.
+  // Recreate the stream (DoCreate() will first shut down an existing stream).
+  // Exit if we ran into an error.
+  const State original_state = state_;
   state_ = kRecreating;
   DoCreate();
   if (!stream_ || state_ == kError)
@@ -397,4 +398,33 @@ void AudioOutputController::OnDeviceChange() {
   }
 }
 
+void AudioOutputController::StartDiverting(AudioOutputStream* to_stream) {
+  if (!message_loop_->BelongsToCurrentThread()) {

[DaleCurtis, 2013/01/02 21:56:44]

This is still odd and inconsistent with the rest of the file. The thread checker
doesn't add anything either since you're always posting the task.

Instead you should break this up into StartDiverting() and DoStartDiverting()
like the rest of the methods which do the same thing.

[miu, 2013/01/03 22:30:42]

Done.

+    DCHECK(divert_thread_checker_.CalledOnValidThread());
+    message_loop_->PostTask(
+        FROM_HERE,
+        base::Bind(&AudioOutputController::StartDiverting, this, to_stream));
+    return;
+  }
+
+  DCHECK(!diverting_to_stream_);
+  diverting_to_stream_ = to_stream;
+  DCHECK_NE(kClosed, state_);

[DaleCurtis, 2013/01/02 21:56:44]

Instead of a DHCECK_NE, shouldn't this be an if (state == kClosed) return before
diverting_to_stream_ is set?

[miu, 2013/01/03 22:30:42]

Done.

+  OnDeviceChange();
+}
+
+void AudioOutputController::StopDiverting() {

[DaleCurtis, 2013/01/02 21:56:44]

Ditto.

[miu, 2013/01/03 22:30:42]

Done.

+  if (!message_loop_->BelongsToCurrentThread()) {
+    DCHECK(divert_thread_checker_.CalledOnValidThread());
+    message_loop_->PostTask(
+        FROM_HERE, base::Bind(&AudioOutputController::StopDiverting, this));
+    return;
+  }
+
+  if (state_ != kClosed) {
+    OnDeviceChange();

[DaleCurtis, 2013/01/02 21:56:44]

This needs a comment since it's subtle that OnDeviceChange will automatically
stop diverting when DoStopCloseAndClearStream() occurs w/ divert_to_stream_ ==
stream_.

[miu, 2013/01/03 22:30:42]

Done.

+    DCHECK(!diverting_to_stream_);
+  }
+}
+
 }  // namespace media