Re-add AC3/EAC3 audio demuxing support

media/formats/mp4/es_descriptor.h

Index: media/formats/mp4/es_descriptor.h
diff --git a/media/formats/mp4/es_descriptor.h b/media/formats/mp4/es_descriptor.h
index 26ca86db2097f5ae5ff10d303b0acb63b4c9efc0..9066291457bb2c83af38f17076e961c6b65b60e7 100644
--- a/media/formats/mp4/es_descriptor.h
+++ b/media/formats/mp4/es_descriptor.h
@@ -21,8 +21,10 @@ namespace mp4 {
 // objectTypeIndication Values. Only values currently in use are included.
 enum ObjectType {
   kForbidden = 0,
-  kISO_14496_3 = 0x40,  // MPEG4 AAC
-  kISO_13818_7_AAC_LC = 0x67  // MPEG2 AAC-LC
+  kISO_14496_3 = 0x40,         // MPEG4 AAC

[ddorwin, 2016/01/08 18:11:02]

dalecurtis agreed that just calling it AAC sounds better. We could move the spec
to the comment if it is useful.

This doesn't need to be done in this CL, but we should be consistent.

[servolk, 2016/01/08 20:02:32]

Ok, will do in a separate CL.

+  kISO_13818_7_AAC_LC = 0x67,  // MPEG2 AAC-LC
+  kAC3 = 0xa5,                 // AC3
+  kEAC3 = 0xa6                 // EAC3 / Dolby Digital Plus
 };
 
 // This class parse object type and decoder specific information from an