Re-add AC3/EAC3 audio demuxing support

media/media_options.gni

Index: media/media_options.gni
diff --git a/media/media_options.gni b/media/media_options.gni
index fa01d0fe64f1e68827a7ae40a5ba182333ef382c..39cc08137f8eee8bdc384972f405108c7cc0e1d2 100644
--- a/media/media_options.gni
+++ b/media/media_options.gni
@@ -48,6 +48,11 @@ declare_args() {
   # Use low-memory buffers on non-Android builds of Chromecast.
   use_low_memory_buffer = is_chromecast && !is_android
 
+  # Enables AC3/EAC3 audio demuxing. This is enabled only on Chromecast, since
+  # it only provides demuxing, and is only useful for AC3/EAC3 audio
+  # pass-through to HDMI sink on Chromecast.
+  enable_ac3_eac3_audio_demuxing = is_chromecast

[ddorwin, 2016/01/08 18:11:02]

I wonder whether we should add "proprietary_codecs &&" to these. This is always
the case for Chromecast, but it would make it clear that there is a dependency
in the build files and code.

[servolk, 2016/01/08 20:02:33]

Done (I've placed is_chromecast first to make it more prominent)

+
   enable_mse_mpeg2ts_stream_parser = is_chromecast
 
   # Enable HEVC/H265 demuxing. Actual decoding must be provided by the