UserAgent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_13_4) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/67.0.3396.87 Safari/537.36

Example URL:
https://twitter.com/googlechrome/status/992155275506286592

Steps to reproduce the problem:
1. Make sure you're logged into twitter (the "more replies" links don't seem to show up otherwise)
2. Go to https://twitter.com/googlechrome/status/992155275506286592
3. Scroll to the bottom and click on the "Show more replies" link (any "more replies" link will reproduce)
4. Press the up or down arrow keys on the keyboard to scroll.

What is the expected behavior?
The page scrolls.

What went wrong?
Nothing happens.

Does it occur on multiple sites: Yes

Is it a problem with a plugin? No 

Did this work before? N/A 

Does this work in other browsers? Yes

Chrome version: 67.0.3396.87  Channel: stable
OS Version: OS X 10.13.4
Flash Version: 

I initially thought this might be the same bug as https://bugs.chromium.org/p/chromium/issues/detail?id=852932, but unlike that bug, this one happens even with SitePerProcess disabled.

I confirmed that this happens with no extensions running, and that the bug does not occur in Firefox or Safari.