iOS and Safari 15.4 / 15.5 crash with css animations

Hi there,

Just wanted to report an issue with Safari on iOS v15.4 / 15.5 that we've run into recently where the browser will crash due to the usage of CSS animations using @keyframes styling rules.

I believe that these issues likely have to due with iOS/Safari's update to WebGL 2.0 / WebGL for Metal.

Specifically in regards to the issue I was experiencing, if there is a child element that has a CSS opacity rule applied to it within a parent element that has a CSS @keyframes animation applied to it, Safari would reload the page and eventually crash after several seconds and display this "A problem repeatedly occurred" error.

If I removed the CSS opacity styling rule from the child element within this parent element that has the @keyframes CSS animation applied to it, OR if I just removed the CSS @keyframes animation styling rule from the parent element itself, this resolved the issue and the crash no longer occurs.

This issue does not appear to affect iPadOS 15.4.1, only iOS 15.4.1 or greater.

(note however that I have not tested with iPadOS greater than 15.4.1 yet but assume it does not have this issue)

There's definitely some bugs that reside in this latest iOS / Safari update and I believe they are all related to this new WebGL 2.0 / WebGL for Metal integration (as per similar issues I read about here and here)