GitLab

- Add content_browsertests in single process mash mode to bots;
- Add a filter file of the failed/flaky tests;

Bug: 874089
Change-Id: I806556b0de0b4ee154d03395a566d0e6610eb5c3
Reviewed-on: https://chromium-review.googlesource.com/1234258Reviewed-by: Ben Pastene <bpastene@chromium.org>
Reviewed-by: James Cook <jamescook@chromium.org>
Commit-Queue: Xiyuan Xia <xiyuan@chromium.org>
Cr-Commit-Position: refs/heads/master@{#592839}