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..f9ce230f86118b1055f167d10dcfabe0139bd10b 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 && proprietary_codecs

[ddorwin, 2016/01/08 20:15:42]

The reason I proposed the other way in PS35 is that proprietary_codecs is the
common prerequisite. For example, if another platform was added, it would be
"proprietary_codecs && (is_chromecast || is_foo)". Written the other way,
someone might add "is_foo || ...", which would be wrong.

[servolk, 2016/01/08 21:55:48]

Done.

+
   enable_mse_mpeg2ts_stream_parser = is_chromecast

[ddorwin, 2016/01/08 20:15:42]

I think it's fine to make the same change here in this CL.

[servolk, 2016/01/08 21:55:48]

Done.

 
   # Enable HEVC/H265 demuxing. Actual decoding must be provided by the