Re-add AC3/EAC3 audio demuxing support

media/media_options.gni

 # Copyright 2014 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 declare_args() {
   # Allows distributions to link pulseaudio directly (DT_NEEDED) instead of
   # using dlopen. This helps with automated detection of ABI mismatches and
   # prevents silent errors.
   link_pulseaudio = false
 
@@ skipping 23 matching lines @@
 
   # TODO(GYP): How to handled the "embedded" use case?
   # Original conditional: (OS=="linux" or OS=="freebsd" or OS=="solaris") and embedded!=1
   if (is_posix && !is_android && !is_mac) {
     use_alsa = true
     if (!use_cras) {
       use_pulseaudio = true
     }
   }
 
+  # Enables AC3/EAC3 audio demuxing. Disabled by default because it's only
+  # demuxing, not decoding. It's of limited use (but can be used to implement
+  # AC3/EAC3 audio pass-through)
+  enable_ac3_eac3_audio_demuxing = false
+
   # Enables the MPEG2-TS stream parser for use with Media Source. Disabled by
   # default since it's not available on the normal Web Platform and costs money.
   enable_mpeg2ts_stream_parser = false
 
   # Enables browser side Content Decryption Modules. Required for android where
   # the typical PPAPI based CDM is not available.
   enable_browser_cdms = is_android
 
   # TODO(GYP): This should be a platform define.
   is_openbsd = false
 }