SDK / exoplayer

Also revert ability to query for a decoder that explicitly
supports tunneling, since in the new design we'll just be
querying the first decoder provided by the MediaCodecSelector
and then reporting what it supports. This is in line with
what we do when reporting support for adaptive switching.

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Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=144315746