Scrolling broken in Firefox (newest pre-release only)

[dx034]

• code-server version: 2.1472-vsc1.38.1
• OS Version: Ubuntu 18.03 LTS

Description

With the newest pre-release, scrolling isn't working in Firefox 69 in any window. Scrolling works fine in Chrome. The bug didn't occur with last week's pre-release. I skipped two pre-releases so I'm not sure which commit introduced the bug.

Steps to Reproduce

1. Use code-server in Firefox

[sr229]

We're gonna be digging a whole lot of history but I think @code-asher has an idea.