GitLab

Add ArcSnapshotRebootNotification that is shown if inside a snapshot
update interval and user is logged in.
SnapshotRebootController tries to reboot the device once user consents
by pressing a restart button.

BUG=b:170187468
TEST=components_unittests
TEST=unit_tests

Change-Id: I3dcae858e8f889aa4be4fc7d5344359488c9d5fc
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2627523Reviewed-by: Hidehiko Abe <hidehiko@chromium.org>
Reviewed-by: Oleksandr Peletskyi <peletskyi@chromium.org>
Commit-Queue: Polina Bondarenko <pbond@chromium.org>
Auto-Submit: Polina Bondarenko <pbond@chromium.org>
Cr-Commit-Position: refs/heads/master@{#844690}