Able to reproduce this issue on latest M-62 i.e. on 62.0.3199.0/9892.0.0 dev-channel Daisy,Kip and Minnie devices.
Adding Stable Blocker as this is a recent Regression , please feel free to remove if not required.
Attaching Actual & Expected Videos for reference

@dmazzoni : please confirm the Issue

Deleted: Actual.mp4 15.7 MB

Actual.mp4 15.7 MB Download

Deleted: Expected.mp4 14.5 MB

	Expected.mp4 14.5 MB View Download

No idea about this one, we should bisect.

Any update on this bug? We are going for a stable RC next week and this is marked as a blocker. 

Whom is the right owner here?

Any update on this one? We are planning to build a R62 stable RC the evening of the 19th, so we would need to have all fixes merged back to 62 in ~24 hours. 

Bisect would be appreciated, otherwise assigning to David.

I did some bisecting and I think 9765.0.0 introduced this, I took a look at the  CLs and I thought crrev.com/c/580667 may be related to this problem, +derat@ can you take a look please?

#6: That change was a fix for a bug where powerd would stop honoring a still-active request to force the display off. If this was a side effect, the root cause of the problem is elsewhere.

I think this is the Chromevox feature tracked at  issue 625741 . David is probably the right person to answer questions about how users are supposed to turn the screen back on.

Note that the API used by Chromevox is calling the SetBacklightsForcedOff, so the screen won't turn back on unless that method is called again to stop forcing the backlights off. There's some more discussion in  issue 760730 .

To be clear, this is the way the feature is supposed to work. Similar features on iOS
screen curtain:
https://www.youtube.com/watch?v=3JySEFcjks0

Android:
dim screen
https://support.google.com/accessibility/android/answer/6006589?hl=en

These features are independent of system brightness settings.

If on Chrome OS, we were actually turning back on the screen again when brightness keys were pressed, then that's unintended.

To mitigate non-ChromeVox users turning on the darken screen feature, we removed the menu options but left the keyboard shortcuts.

Note that turning off ChromeVox *should* turn back on the screen.

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/fcbf4d7f59919810aa9be44cdf0660f5b5e8492b

commit fcbf4d7f59919810aa9be44cdf0660f5b5e8492b
Author: David Tseng <dtseng@chromium.org>
Date: Fri Oct 20 17:53:13 2017

Remove darken and undarken screen from chromeVox menus

Bug:  760499 
Cq-Include-Trybots: master.tryserver.chromium.linux:closure_compilation
Change-Id: Ic2b48fee1d9e31a8e44123102676df1027653be4
Reviewed-on: https://chromium-review.googlesource.com/728939
Reviewed-by: Dominic Mazzoni <dmazzoni@chromium.org>
Commit-Queue: David Tseng <dtseng@chromium.org>
Cr-Commit-Position: refs/heads/master@{#510483}
[modify] https://crrev.com/fcbf4d7f59919810aa9be44cdf0660f5b5e8492b/chrome/browser/resources/chromeos/chromevox/common/command_store.js

Should we merge this back to 63/62? Consider this merge approved if so.

We build the R62 stable RC tomorrow, we need a fix in the next 24 hours.

If we want this change, can we merge it today?

I don't think this is a release blocker in any case. Thanks!

SGTM, removing RBS, thanks!

This issue has been approved for a merge. Please merge the fix to any appropriate branches as soon as possible!

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This issue has been approved for a merge. Please merge the fix to any appropriate branches as soon as possible!

If all merges have been completed, please remove any remaining Merge-Approved labels from this issue.

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This issue hasn't been updated in the last 6 weeks, so removing its merge approval label. Please re-request a merge if needed.

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Too late to merge into M63.