GitLab

This doesn't force use of the SSL repo, but prevents overwriting the
repo config if a user manually changes it to use HTTPS.

R=thestig@chromium.org, thestig@google.com
BUG=433450,474100

Review URL: https://codereview.chromium.org/1068323002

Cr-Commit-Position: refs/heads/master@{#324317}