Good Build: 64.0.3247.0
Bad Build:  64.0.3248.0

You are probably looking for a change made after 510939 (known good), but no later than 510940 (first known bad).
CHANGELOG URL:
The script might not always return single CL as suspect as some perf builds might get missing due to failure.
https://chromium.googlesource.com/chromium/src/+log/a659a1b325746dee933e7d0590de1aa1ee25f633..0cafb39dcf12fdd92433482e856cf8132994e64b

Suspecting: https://chromium.googlesource.com/chromium/src/+/0cafb39dcf12fdd92433482e856cf8132994e64b
Could you please check whether this is caused with respect to your change, if not please help us in assigning it to the right owner.

Adding RB Label as this is a recent Regression. Please remove if not required.
Thank You.

In the video, it looks like the user uses the arrow keys to move to the "Always allow sound..." option, but doesn't actually select it (by pressing enter or the spacebar), so it doesn't get saved. If the user hits the spacebar or enter key, the option is actually selected and when the user presses the "Done" button, all works as anticipated. This is how it works for all permissions, so my assumption is that this is WAI.

Thanks!