[Chromecast] Add option to hide streams from stream count

Change-Id: I300499d16e732092e206abb746146b25c3f224c4
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1891135Reviewed-by: Yuchen Liu <yucliu@chromium.org>
Commit-Queue: Kenneth MacKay <kmackay@chromium.org>
Cr-Commit-Position: refs/heads/master@{#710929}

chromecast/media/audio/mixer_service/mixer_service.proto

@@ -52,6 +52,9 @@ message OutputStreamParams {
   // If |true|, playback will not start until a start timestamp has been
   // provided via a SetStartTimestamp message.
   optional bool use_start_timestamp = 13;
+
+  // If |true|, this stream will not be included in the mixer's stream counts.
+  optional bool ignore_for_stream_count = 14;
 }
 
 // Indicates that we want to start playing the sample with PTS |start_pts|

chromecast/media/cma/backend/mixer/mixer_input_connection.cc

@@ -149,6 +149,7 @@ MixerInputConnection::MixerInputConnection(
     const mixer_service::OutputStreamParams& params)
     : mixer_(mixer),
       socket_(std::move(socket)),
+      ignore_for_stream_count_(params.ignore_for_stream_count()),
       fill_size_(GetFillSize(params)),
       num_channels_(params.num_channels()),
       input_samples_per_second_(params.sample_rate()),
@@ -466,7 +467,7 @@ int MixerInputConnection::playout_channel() {
 
 bool MixerInputConnection::active() {
   base::AutoLock lock(lock_);
-  return !paused_;
+  return !ignore_for_stream_count_ && !paused_;
 }
 
 void MixerInputConnection::WritePcm(scoped_refptr<net::IOBuffer> data) {

chromecast/media/cma/backend/mixer/mixer_input_connection.h

@@ -133,6 +133,7 @@ class MixerInputConnection : public mixer_service::MixerSocket::Delegate,
   StreamMixer* const mixer_;
   std::unique_ptr<mixer_service::MixerSocket> socket_;
 
+  const bool ignore_for_stream_count_;
   const int fill_size_;
   const int num_channels_;
   const int input_samples_per_second_;