Account for partial reads in PacketedBio.

This fixes test flakiness on Windows.

BUG=467767

Change-Id: Ie69b5b43ddd524aadb15c53705f6ec860e928786
Reviewed-on: https://boringssl-review.googlesource.com/4001
Reviewed-by: Adam Langley <agl@google.com>
1 file changed