Re-add AC3/EAC3 audio demuxing support

media/base/audio_decoder_config.cc

Index: media/base/audio_decoder_config.cc
diff --git a/media/base/audio_decoder_config.cc b/media/base/audio_decoder_config.cc
index 213cb10edc41881a16b8e5cdb67cf0b43e685503..1c0a58299d8efec71e07b82549e624641064191e 100644
--- a/media/base/audio_decoder_config.cc
+++ b/media/base/audio_decoder_config.cc
@@ -100,6 +100,10 @@ std::string AudioDecoderConfig::GetHumanReadableCodecName() const {
       return "unknown";
     case kCodecAAC:
       return "aac";
+    case kCodecAC3:

[ddorwin, 2015/11/25 22:24:07]

Keep the cases in the same order as the enum.

[servolk, 2015/12/03 00:56:14]

Done.

+      return "ac3";
+    case kCodecEAC3:
+      return "eac3";
     case kCodecMP3:
       return "mp3";
     case kCodecPCM: