GitLab

Add SnapshotSessionController to control MGS with loaded ARC
data snapshot and ARC data snapshot update flow.
Consider MGS as failed if not 100% of required ARC apps are installed in
5 mins.

BUG=b:161221001
TEST=components_unittests
TEST=browser_tests

Change-Id: I47b5021df115b4af6aa3fba543a34daf192c2fd7
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2550839Reviewed-by: Hidehiko Abe <hidehiko@chromium.org>
Reviewed-by: Roman Sorokin [CET] <rsorokin@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@{#835132}