GitLab

This adds master mixins for:
* chromium
* chromium.chromedriver
* chromium.lkgr
* chromium.swarm

Bug: 840631
Change-Id: Ia615d68243c114bc61b44ec2179e1b5830ea02d5
Reviewed-on: https://chromium-review.googlesource.com/1063167Reviewed-by: Andrii Shyshkalov <tandrii@chromium.org>
Commit-Queue: Ryan Tseng <hinoka@chromium.org>
Cr-Commit-Position: refs/heads/master@{#559373}