Currently, pending stream offset changes are kept until an output buffer
timestamp surpasses the next pending stream offset. However, this is
problematic if the next stream offset overlaps with the current output
buffer sample times (e.g. because the next stream starts at a non-zero start
time).
To correctly time the switch to the next stream offset, this change keeps
the timestamp of the last queued input sample as switch point. And we only
switch to the new offset after an output sample timestamp reached this switch
point.
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Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=192736637
0a68d1f09c