UserAgent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_13_6) AppleWebKit/605.1.15 (KHTML, like Gecko) Version/12.0 Safari/605.1.15

Steps to reproduce the problem:
1. Open Chrome 69.x on a Mac
2. https://www.03sq.net/kenza/prototype-testing/0.0.12/background.html
3. Observe background loads sluggishly and plays at 1-2 FPS

What is the expected behavior?
Background plays at 20fps-30fps depending on hardware.

What went wrong?
This problem only seems to affect Chrome on OSX. In Chrome 68.x it was fine, I updated to Chrome 69 this morning and now I have this issue. I have tried and can reproduce this on a Mac Pro as well as a MacBook Pro.
Chrome 69 on Windows appears to still work correctly.

I tried loading Chrome without extensions and got the following error message:
scott$ /Applications/Google\ Chrome.app/Contents/MacOS/Google\ Chrome -args -disable-extensions
AVDCreateGPUAccelerator: Error loading GPU renderer
(MacPro, 3 GHz 8-Core Intel Xeon E5, AMD FirePro D700 6144 MB)

I updated to the beta channel to see if I still got the same behaviour and yes I do, just no console error message. (Chrome 69.0.3497.81)

I tried in both Chrome Dev channel (70.0.3538.9) and Chrome Canary (71.0.3549.0) and it's not reproducible - so it may be a fixed issue?

Did this work before? Yes Chrome 68

Does this work in other browsers? Yes

Chrome version: 69.0.3497.81  Channel: stable
OS Version: OS X 10.13.6
Flash Version: 

More than happy to talk to someone about this to explain exactly what I'm doing and/or provide source code - basically am taking frames from a small video file, rendering them to an offscreen canvas, getting the pixel data from each pixel and plotting those pixels as circles in canvas. Works in everything from IE11 to Firefox