GitLab

Ensure that the test launcher can run a test multiple times in parallel
to enable us finding flaky tests faster.

Also add documentation for --gtest-repeat and --gtest-break-on-failure.

R=erikchen@chromium.org
BUG=976795

Change-Id: I767a618fda6ad8f7424b43b0bf1a06b5238f127a
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1667313
Commit-Queue: Alexander Timin <altimin@chromium.org>
Reviewed-by: Ilia Samsonov <isamsonov@google.com>
Cr-Commit-Position: refs/heads/master@{#804465}