Chrome OS 11151.24.0, 71.0.3578.45

Please specify Cr-* of the system to which this bug/feature applies (add
the label below).

Steps To Reproduce:
(1)Set single-day screen time and wait till usage time reac 
(2)Play youtube kids videos 
(3)Wait till usage time reaches to ends

Expected Result:
Notification should pop up on the screen while watching videos with full screen-mode.

Actual Result:
Screen locked without notification popup while watching videos on the full screen mode.


How frequently does this problem reproduce? (Always, sometimes, hard to
reproduce?)

What is the impact to the user, and is there a workaround? If so, what is
it?

Please provide any additional information below. Attach a screen shot or
log if possible.

For graphics-related bugs, please copy/paste the contents of the about:gpu
page at the end of this report.