SDK / exoplayer

This class can accommodate extra information that may potentially
be specified by TrackSelectors in the future (e.g. configuration
for renderers). Even if we don't do this, it's cleaner to have a
proper class and an info field to refer to, as opposed to using a
Pair.

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Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=144428963