Convert enable_mpeg2ts into a new-style buildflag

media/media_options.gni

Index: media/media_options.gni
diff --git a/media/media_options.gni b/media/media_options.gni
index 62401b1eb42bdc0a7c07ea3f693784823ea7c986..fa01d0fe64f1e68827a7ae40a5ba182333ef382c 100644
--- a/media/media_options.gni
+++ b/media/media_options.gni
@@ -48,10 +48,7 @@ declare_args() {
   # Use low-memory buffers on non-Android builds of Chromecast.
   use_low_memory_buffer = is_chromecast && !is_android
 
-  # Enables the MPEG2-TS stream parser for use with Media Source. Disabled by
-  # default (except on Chromecast) since it's not available on the normal Web
-  # Platform and costs money.
-  enable_mpeg2ts_stream_parser = is_chromecast
+  enable_mse_mpeg2ts_stream_parser = is_chromecast

[ddorwin, 2016/01/05 18:59:56]

I see you moved this and it is no longer inside buildflag_header with the
define. Is there a reason for this? Does it matter for the new mechanism?

[brettw, 2016/01/05 19:03:51]

Like C, it doesn't matter where the variable is defined as long as it's defined
by the time you use it.

[ddorwin, 2016/01/05 19:17:24]

Thanks. I guess it was more a question of style and proximity.

 
   # Enable HEVC/H265 demuxing. Actual decoding must be provided by the
   # platform. Enable by default for Chromecast.