Change DeviceAutoUpdateTimeRestrictions to JSON

Refactor DeviceAutoUpdateTimeRestrictions to use a JSON string instead
of a proto.

BUG=chromium:852860
TEST=None

Change-Id: Ic5174ad705b3cf59dfbbfc5713c231bf7f057a0f
Reviewed-on: https://chromium-review.googlesource.com/1109264
Reviewed-by: Lutz Justen <ljusten@chromium.org>
Reviewed-by: Maksim Ivanov <emaxx@chromium.org>
Commit-Queue: Maksim Ivanov <emaxx@chromium.org>
Cr-Original-Commit-Position: refs/heads/master@{#570928}
Cr-Mirrored-From: https://chromium.googlesource.com/chromium/src
Cr-Mirrored-Commit: 6ca6c93c28c1cebb7bb68e81542b290a853e0eb7
1 file changed