SDK / exoplayer

Follow-up to a comment on
https://github.com/androidx/media/commit/ac8e418f3d28876ed38b0d6465793e4cdfb273ba
Buffers that are useful to pass to the sample/passthrough pipeline
should either contain data or the end of input flag. Otherwise, passing
these buffers along is unnecessary and may even cause the decoder to
allocate a new input buffer which is wasteful.

PiperOrigin-RevId: 411060709