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 0dcc76aca062b19bbdfb941088d053c1d1970ad3..fdc05876013fcfd130922a760ec299b084bd02b6 100644
--- a/media/audio/audio_output_device.cc
+++ b/media/audio/audio_output_device.cc
@@ -476,12 +476,23 @@ void AudioOutputDevice::AudioThreadCallback::Process(uint32_t pending_data) {
            << " frames_delayed(pre-round):" << frames_delayed
            << " frames_skipped:" << frames_skipped;
 
+  output_bus_->set_is_raw_format(audio_parameters_.IsRawFormat());

[DaleCurtis, 2016/11/04 21:24:53]

What happens if you output zeros when in bitstreaming mode? Is that still
silence? If so I think it makes sense to not modify AudioBus and just always
send even multiples of 4 bytes in frames. Padding the last buffer with zeros.

[chcunningham, 2017/06/14 20:03:08]

Also curious about the meaning of zeroes.

+  if (audio_parameters_.IsRawFormat()) {
+    // 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(output_bus_.get(), std::round(frames_delayed),
                            frames_skipped);
+  buffer->params.frames = output_bus_->frames();
+  buffer->params.data_size = output_bus_->data_size();
 }
 
 bool AudioOutputDevice::AudioThreadCallback::