GitLab

Original CL: https://codereview.chromium.org/512693003/

This was reverted because LocationBarBrowserTest.PageActionUITest is flaky on
Mac. Resubmit this, but with the flaky test disabled on mac.

BUG=408261
BUG=410866

Review URL: https://codereview.chromium.org/543783002

Cr-Commit-Position: refs/heads/master@{#293364}