Support (E)AC3 passthrough

media/filters/audio_renderer_algorithm.cc

Index: media/filters/audio_renderer_algorithm.cc
diff --git a/media/filters/audio_renderer_algorithm.cc b/media/filters/audio_renderer_algorithm.cc
index fe30e80add0c81ac61903bb7731719dd53fa2a60..f214c00cc2256cdbec0e993193fd90140670bd58 100644
--- a/media/filters/audio_renderer_algorithm.cc
+++ b/media/filters/audio_renderer_algorithm.cc
@@ -77,6 +77,7 @@ static const int kStartingCapacityForEncryptedInMs = 500;
 AudioRendererAlgorithm::AudioRendererAlgorithm()
     : channels_(0),
       samples_per_second_(0),
+      is_bitstream_format_(false),
       muted_partial_frame_(0),
       capacity_(0),
       output_time_(0.0),
@@ -98,6 +99,7 @@ void AudioRendererAlgorithm::Initialize(const AudioParameters& params,
 
   channels_ = params.channels();
   samples_per_second_ = params.sample_rate();
+  is_bitstream_format_ = params.IsBitstreamFormat();
   initial_capacity_ = capacity_ = std::max(
       params.frames_per_buffer() * 2,
       ConvertMillisecondsToFrames(is_encrypted
@@ -157,6 +159,14 @@ int AudioRendererAlgorithm::FillBuffer(AudioBus* dest,
   DCHECK_GT(playback_rate, 0);
   DCHECK_EQ(channels_, dest->channels());
 
+  dest->set_is_bitstream_format(is_bitstream_format_);

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

this block too could use some documentation for future readers about why we skip
logic below.

[AndyWu, 2017/08/02 01:43:41]

Done.

+  if (is_bitstream_format_) {
+    dest->set_data_size(0);

[DaleCurtis, 2017/06/15 21:46:32]

Why?

[AndyWu, 2017/08/02 01:43:40]

Removed.

+    dest->set_frames(0);
+
+    return audio_buffer_.ReadFrames(requested_frames, dest_offset, dest);
+  }
+
   // Optimize the muted case to issue a single clear instead of performing
   // the full crossfade and clearing each crossfaded frame.
   if (playback_rate < kMinPlaybackRate || playback_rate > kMaxPlaybackRate) {