Google Chrome	72.0.3593.0 (Official Build) dev (64-bit)
Firmware Version Google_Caroline.7820.384.0

Steps to repro:
# Start ChromeVox with ctrl + alt + z
# Enable dark screen/screen curtain with search + shift + brightness up 

It would be nice to have a dialog appear telling you how to turn the screen curtain back off just like how dialogs appear for ChromeVox, the magnifers, and High Contrast with instructions for turning it off. '

Note: blocked by bug 916373 - you need to be able to turn off the feature before adding this dialog