I noticed the animation technique we are using for the Photon browser chrome animations just stopped working. Here's a simple example: https://jsfiddle.net/sfoster/hc052a8y/ An inner element has the width of the entire image and an outer element uses overflow:hidden to clip to a frame width/height, and the animation advances through the frames using transform: translateX(...) on the inner element. Clicking on the arrow should produce a smooth/jank-free animation that runs on the compositor. In todays nightly it looks like we just see the first frame or so. Mozregression suggests this push: https://hg.mozilla.org/integration/mozilla-inbound/pushloghtml?fromchange=958d2a5d10091401fd5e900e8e063d21940c137e&tochange=7f894f791cdf170d788507d0eff30024ce699523

:mattwoodrow, your commits in that pushlog there look relevant? Also flagging :mstange as he's been working with us on this specific technique and was also a reviewer on one of the changes so might have useful context.

This page also shows a demo, http://msuja.ws/svg.html

This is probably a duplicate of one of the regression bugs that have been filed against bug 1361970 today.

Dupe of bug #1373479