If we don't have resolutions (and therefore cannot determine
pixel counts) then use bitrate as a tie breaker instead. Also
use pixel count as a tie breaker if pixel counts are known
but equal. Streams with known pixel counts will always be
preferred over streams without.
Issue: #2343
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Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=145269968
