Refactor MediaResource to be multi-stream capable

chromecast/media/service/cast_renderer.cc

Index: chromecast/media/service/cast_renderer.cc
diff --git a/chromecast/media/service/cast_renderer.cc b/chromecast/media/service/cast_renderer.cc
index 42964baf9931ca51a38fc5d8e885dda2567a16da..0ae827aa310915caadf14a6f9bbdf1dde1df145d 100644
--- a/chromecast/media/service/cast_renderer.cc
+++ b/chromecast/media/service/cast_renderer.cc
@@ -91,9 +91,23 @@ void CastRenderer::Initialize(::media::MediaResource* media_resource,
   pipeline_->SetClient(pipeline_client);
   pipeline_->Initialize(load_type, std::move(backend));
 
+  // TODO(servolk): Implement support for multiple streams. For now use the
+  // first enabled audio and video streams to preserve the existing behavior.
+  std::vector<::media::DemuxerStream*> streams = media_resource->GetStreams();
+  ::media::DemuxerStream* audio_stream = nullptr;
+  ::media::DemuxerStream* video_stream = nullptr;
+  for (const auto& stream : streams) {
+    if (!audio_stream && stream->enabled() &&
+        stream->type() == ::media::DemuxerStream::AUDIO) {
+      audio_stream = stream;
+    }
+    if (!video_stream && stream->enabled() &&
+        stream->type() == ::media::DemuxerStream::VIDEO) {
+      video_stream = stream;
+    }
+  }
+
   // Initialize audio.
-  ::media::DemuxerStream* audio_stream =
-      media_resource->GetStream(::media::DemuxerStream::AUDIO);
   if (audio_stream) {
     AvPipelineClient audio_client;
     audio_client.wait_for_key_cb = base::Bind(
@@ -118,8 +132,6 @@ void CastRenderer::Initialize(::media::MediaResource* media_resource,
   }
 
   // Initialize video.
-  ::media::DemuxerStream* video_stream =
-      media_resource->GetStream(::media::DemuxerStream::VIDEO);
   if (video_stream) {
     VideoPipelineClient video_client;
     video_client.av_pipeline_client.wait_for_key_cb = base::Bind(