GitLab

Give a little info about default buttons so that consumers think about
whether or not they're a good thing.

BUG=884831
R=pkasting@chromium.org

Change-Id: I9f65cfdfc349fb71a270973d416decd5528c8e88
Reviewed-on: https://chromium-review.googlesource.com/1251082Reviewed-by: Peter Kasting <pkasting@chromium.org>
Reviewed-by: Michael Wasserman <msw@chromium.org>
Commit-Queue: Greg Thompson <grt@chromium.org>
Cr-Commit-Position: refs/heads/master@{#595306}