Add DeviceAutoUpdateTimeRestrictions to device_settings_provider

Add DeviceAutoUpdateTimeRestrictions policy to the device settings
provider so that the policy can be accessed by about handler to
notify users when autoupdates are disabled (CL:1130503).

BUG=chromium:852860
TEST=unit_tests

Change-Id: I7d72973220041e98b5a2c3af978cbcd07728ba88
Reviewed-on: https://chromium-review.googlesource.com/1128440
Commit-Queue: Adolfo Higueros <adokar@google.com>
Reviewed-by: Steven Bennetts <stevenjb@chromium.org>
Reviewed-by: Lutz Justen <ljusten@chromium.org>
Cr-Commit-Position: refs/heads/master@{#573811}
4 files changed