One-line fix up for review at http://crrev.com/c/580667.

The following revision refers to this bug:
  https://chromium.googlesource.com/chromiumos/platform2/+/e6a71fde986a89463dcdc57c97c6b0e35026bd4c

commit e6a71fde986a89463dcdc57c97c6b0e35026bd4c
Author: Daniel Erat <derat@chromium.org>
Date: Fri Jul 21 04:21:23 2017

power: Don't turn forced-off screen on for ambient light.

Fix a bug where changes to ambient light could force the
screen on after it had been forced off by a tablet-style
power button.

BUG= chromium:747165 ,b:63895686
TEST=added unit test; also manual: cover ALS, tap power
     button to turn screen off, uncover ALS and check that
     screen remains off even when ALS is in direct sunlight

Change-Id: If045c70f1a6d8619a09449995c3a3da28ad00734
Reviewed-on: https://chromium-review.googlesource.com/580667
Commit-Ready: Dan Erat <derat@chromium.org>
Tested-by: Dan Erat <derat@chromium.org>
Reviewed-by: Qiang(Joe) Xu <warx@chromium.org>

[modify] https://crrev.com/e6a71fde986a89463dcdc57c97c6b0e35026bd4c/power_manager/powerd/policy/internal_backlight_controller_unittest.cc
[modify] https://crrev.com/e6a71fde986a89463dcdc57c97c6b0e35026bd4c/power_manager/powerd/policy/internal_backlight_controller.cc

Your change meets the bar and is auto-approved for M61. Please go ahead and merge the CL to branch 3163 manually. Please contact milestone owner if you have questions.
Owners: amineer@(Android), cmasso@(iOS), ketakid @(ChromeOS), govind@(Desktop)

For more details visit https://www.chromium.org/issue-tracking/autotriage - Your friendly Sheriffbot

yt looks like the release-R61-9765.B branch was cut later than planned, so this appears to already be present in M61.