Found in

• Firefox 107.0b2;

Affected versions

• Firefox 107.0b2;
• Nightly 108.0a1;
• Firefox 106.0;

Tested platforms

• Windows 10;
• macOS 11;
• Ubuntu;

Affected platforms

• WIndows 10;

Unaffected platforms

• macOS 11;
• Ubuntu 20;

Steps to reproduce

1. Launch Firefox.
2. Go to https://testdrive-archive.azurewebsites.net/Graphics/CanvasPinball/Default.html
3. Use the keyboard arrows to play.

Expected result

• Clean, fast rendering.

Actual result

• Laggy rendering.

Regression range

• Will look for one ASAP.

Notes

• Rendering looks fine in Chrome. Please see attached video for more details.

Profile: https://share.firefox.dev/3CMSpNO

The profile doesnt show any gfx related stuff.
The speed is improved if you enable the profiler. This is a known phenomenon, and from what i remember :mstange explanation, is an obsolete method of animation.
IMO, this bug should be resolved invalid.

We regularly test this website and the issue is only seen on Windows - site renders well on macOS, Ubuntu and Chrome. We assumed it would be a bug given the circumstances.

One of the regression windows I could find:
https://hg.mozilla.org/integration/mozilla-inbound/pushloghtml?fromchange=83f3573ea26840208086aa5bd7d41aff37a0ddf1&tochange=7c6116ac71e954805dccf3146d6fffcf28bbc0cf

Tried to narrow the regression for this issue but I couldn't reach any conclusive result - on my machine I could reproduce the laggy rendering all the way to Firefox 50 (sometimes the lagging improves from one hit to the next one).

I've also investigated this issue was about to say it appears not to be a regression, but then I've noticed a build with slightly better performance around branch 50. After performing a mozregression investigation I could provide these results:
Tested mozilla-central build: 2018-05-01 (verdict: g)
Tested mozilla-central build: 2018-05-02 (verdict: b)