Re-add AC3/EAC3 audio demuxing support

content/content_tests.gypi

 # Copyright (c) 2013 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.
 
 {
   'variables': {
     'layouttest_support_content_sources': [
       'public/test/layouttest_support.h',
       'public/test/nested_message_pump_android.cc',
       'public/test/nested_message_pump_android.h',
@@ skipping 1537 matching lines @@
             ['OS=="mac"', {
               'dependencies': [
                 'content_shell',  # Needed for Content Shell.app's Helper.
               ],
               'sources': [
                 'renderer/external_popup_menu_browsertest.cc',
               ],
             }],
             ['chromecast==1', {
               'defines': [
+                'ENABLE_AC3_EAC3_DEMUXING',
                 'ENABLE_HEVC_DEMUXING',
               ],
             }],
             ['use_aura==1 or toolkit_views==1', {
               'dependencies': [
                 '../ui/events/events.gyp:events_test_support',
               ],
             }],
             ['use_aura!=1 and OS!="mac"', {
               'sources!' :[
@@ skipping 647 matching lines @@
                   'content_unittests_apk.isolate',
                 ],
               },
             ],
           },
         ],
       ],
     }],
   ],
 }