Chrome Version       : 66.0.3359.139
OS Version: 4.9.0-6-amd64
URLs (if applicable) : A local file:// URL, with roughly the same contents as https://www.w3.org/TR/appmanifest/
Other browsers tested: None

What steps will reproduce the problem?
1. Load the page.
2. I used the page for quite some time before problem manifested.
3. Scroll up and down.

What is the expected result?
Nothing out of the ordinary.

What happens instead of that?
Black squares are rendered on the page at random places (see video*). Every frame of scrolling re-randomizes it. When you stop scrolling it stays put.

I experienced this for a few minutes, just in one tab. Then eventually, the black squares showed up less and less (you can see the tail end of this in the video) and then eventually the problem stopped without me having to refresh or anything.

Cannot reproduce any more.

* Video took too long to upload and ruined bug report. I'm trying to upload a smaller version but I'll post this first.