GitLab

Use new method ServiceConnection::FlushForTesting instead of
RunUntilIdle.

Change-Id: Idfa4a5fdd3eb8ab43be0d5ed527e334a6401c821
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2398624Reviewed-by: Mahmoud Gawad <mgawad@google.com>
Commit-Queue: Oleh Lamzin <lamzin@google.com>
Cr-Commit-Position: refs/heads/master@{#805657}