This adds a new function to key AdaptationSets based on the
characteristics that require separate sets.
With this, we are now able to package multi-codec assets at once
(AVC1/MP4 and VP9/WebM in the same manifest, but in different
AdaptationSets).
Fixes b/27534371
Change-Id: Ie82fd096d2ef99fd23e323d60fd0849b1e8d7500
Additionally, for XML schema correctness, convert ISO-639-2 language
tags (three-letter codes) to ISO-639-1 tags (two-letter codes) when
possible. This follows BCP-47, which says to always use the shortest
language tag when there are multiple possibilities.
b/18613148
Change-Id: I120fb7b42ac4da5feb4ca046bba93d9e58acd7a9
Kongqun Yang
Joey Parrish
Rintaro Kuroiwa