Support (E)AC3 passthrough

media/audio/audio_output_device.cc

Index: media/audio/audio_output_device.cc
diff --git a/media/audio/audio_output_device.cc b/media/audio/audio_output_device.cc
index 1013ce6ad731a33aae3f05b0d4c83eef0c94ad40..90c3c3480ad60042507d6be23b34e43d390cc309 100644
--- a/media/audio/audio_output_device.cc
+++ b/media/audio/audio_output_device.cc
@@ -494,12 +494,23 @@ void AudioOutputDevice::AudioThreadCallback::Process(uint32_t control_signal) {
   DVLOG(4) << __func__ << " delay:" << delay << " delay_timestamp:" << delay
            << " frames_skipped:" << frames_skipped;
 
+  output_bus_->set_is_bitstream_format(audio_parameters_.IsBitstreamFormat());

[DaleCurtis, 2017/06/15 21:46:31]

if (audio_parameters_.IsBitstreamFormat()) {
  output_bus_->set_is_bitstream_format(true);
  output_bus_->set_data_size(0);
  output_bus_->set_frames(audio_parameters_.frames_per_buffer());
}

[AndyWu, 2017/08/02 01:43:39]

Done.

+  if (audio_parameters_.IsBitstreamFormat()) {
+    // Reset the data size and frame count.
+    // For compressed audio formats, the data size and frame count will be
+    // updated by |render_callback_|.
+    output_bus_->set_data_size(0);
+    output_bus_->set_frames(audio_parameters_.frames_per_buffer());
+  }
+
   // Update the audio-delay measurement, inform about the number of skipped
   // frames, and ask client to render audio.  Since |output_bus_| is wrapping
   // the shared memory the Render() call is writing directly into the shared
   // memory.
   render_callback_->Render(delay, delay_timestamp, frames_skipped,
                            output_bus_.get());
+  buffer->params.frames = output_bus_->frames();

[DaleCurtis, 2017/06/15 21:46:31]

Hmm, this is always audio_parameters_.frames_per_buffer() ? Is that a mistake?
Otherwise there's no point in sending this information over.

[AndyWu, 2017/08/02 01:43:39]

To make things clear, I changed to GetBitstreamFrames(). It should be PCM frame
count of a compressed audio frame.

+  buffer->params.data_size = output_bus_->data_size();
 }
 
 bool AudioOutputDevice::AudioThreadCallback::