GitLab

Bug was detected while working on stress test:
When part of the data is available and we want to read more,
we need to start not from initial 'pos' but shift to the position
after the available data! The original code always started to read
from the initial position - thus reading some data twice.

Also some cleanup done.

BUG: b:177439641
Change-Id: I59c9d36f97d2a7193ff0d211c61f5afb7cf2d60b
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2626102Reviewed-by: Zach Trudo <zatrudo@google.com>
Commit-Queue: Leonid Baraz <lbaraz@chromium.org>
Auto-Submit: Leonid Baraz <lbaraz@chromium.org>
Cr-Commit-Position: refs/heads/master@{#843284}