GitLab

Add SnapshotHoursPolicyService to handle policy changes.

BUG=b:170187468
TEST=components_unittests

Change-Id: I1918d55d6e53b0085473f7bf650cf949767ed4b8
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2514148Reviewed-by: Roman Sorokin [CET] <rsorokin@chromium.org>
Reviewed-by: Sergey Poromov <poromov@chromium.org>
Reviewed-by: Yusuke Sato <yusukes@chromium.org>
Commit-Queue: Polina Bondarenko <pbond@chromium.org>
Auto-Submit: Polina Bondarenko <pbond@chromium.org>
Cr-Commit-Position: refs/heads/master@{#825794}