Retested in Chrome OS:
72.0.3590.0 (Official Build) dev (64-bit) (cohort: Dev)
Firmware Version: Google_Cave.7820.384.0
Not able to recreate the above issue, ChromeVox works fine.
I did notice that while linear navigation using up and down arrow key to traverse through the various options in accessibility 
for ex: Accessibility>Comments>Speak Comments
The screen reader reads aloud the options however the menu options get white when you press down arrow key.

Workaround for the white to go is when you press the up arrow key.

This also repros with Jaws 2019.
Here is the output from Bisect:
You are probably looking for a change made after 607148 (known good), but no later than 607153 (first known bad).
CHANGELOG URL:
  https://chromium.googlesource.com/chromium/src/+log/ee337661804945f198019e9a627f5957f0f0221d..43e45d3b87ee87ce9d10518d5f3a5ec0884d07b5

My change looks like the most likely culprit here. Taking a look.

I suspect this is around aria-activedescendant update notifications. Digging into that...

Hi aboxhall@, I just wanted to let you know I saw some more odd behavior with the a11y menu options, this time things visually not appearing when they should. I don't think it's related to this bug specifically, but I figured I'd let you know just in case. Please see b/120684385 thanks! 

Thanks Laura!

I'm also curious whether the behaviour in this bug still reproduces now that I've reverted the change we thought was the most likely culprit.

Version 72.0.3626.7 (Official Build) dev (64-bit)
Looks like this no longer repros. Thanks aboxhall@!