GitLab

Allow user to change screen brightness defined by screen brightness policy.
User defined brightness value will be preserved till the end of the user session,
even if policy gets updated. The policy brightness values will not be sent to
power manager in that situation.

Bug: 890068, 310429
Test: chromeos_unittests and manually with local policy server
Change-Id: Ia048b4e328d739347cff7b49a0128db7869165a3
Reviewed-on: https://chromium-review.googlesource.com/c/1285730
Commit-Queue: Aga Wronska <agawronska@chromium.org>
Reviewed-by: Dan Erat <derat@chromium.org>
Reviewed-by: Steven Bennetts <stevenjb@chromium.org>
Cr-Commit-Position: refs/heads/master@{#600852}