Test-case is reduced from https://codepen.io/JeremiePat/full/GVKxYa / https://twitter.com/JeremiePat/status/1151501718624047104, with a poor attempt and making the animations longer.
It spends a lot of time in the compositor, and during layer building. Probably we can try to do something better.
Here's a profile on a clean profile:
Will get a WR profile in a second.
WR profile: https://perfht.ml/2XWfQxE
Though nothing stands out, the animation is still very janky.
On Mac with WebRender https://perfht.ml/2Y8NlAZ the biggest problem looks like malloc contention. This is presumably because of https://hg.mozilla.org/mozilla-central/rev/d9efe6d06931
Unlikely to get anything for 70
I am still seeing a lot of malloc contention on this test case, caused by many nested filters .