I think this is the root cause of bug 1379203, at least, and may be related to bug 1371450 too. I'll attach a test-case that shows the a few links rotating normal restyles (one element should be green at a time). When there's a transform animation in effect (you can click the button to trigger one), if you select some text under the <div id="container">, for example, you eventually end up with multiple green links. In a debug build, this also happens to trigger the "lazy computation forbidden" assertion. This is, I think, due to multiple things: * The slippery handling of element snapshots described in bug 1378064 comment 15. * The fact that the post-traversal for animations follows _both_ the animation dirty descendants bit and the normal dirty descendants bit, regardless of the kind of restyles we're doing. This makes us update the styles before the normal traversal I think, and makes us throw away all the restyle state of elements _not_ affected by animations. This is definitely wrong, but I need more info about how all this is supposed to work with the snapshot stuff, etc, in order to figure out what the correct fix is.

In this test-case, you just have to click on the other non-active links, though it reproduces less frequently than changing the DOM content of the container and selecting it.

I'd never thought that my loading circle could be the cause. That's why all my attempts to make a reduced test case didn't work. Thanks so much!

(In reply to Darkspirit from comment #3) > I'd never thought that my loading circle could be the cause. That's why all > my attempts to make a reduced test case didn't work. Thanks so much! Thank _you_ for pointing me to the problematic page! That was way easier to reduce than Inbox, I'd probably have given up on reducing Inbox actually :-)

Blocking stylo-site-issues as this will affect our website.

(Darkspirit from bug 1380543 comment 7) > Now I tried it with a try build from bug 1371450 comment 13: > https://treeherder.mozilla.org/#/jobs?repo=try&revision=2deb83ce288532ce5f2b1534ffe6623b6ad9a9b2 > > Linux x64 Stylo opt > tc[tier2] > B > target.tar.bz2 (stylo is enabled by default) With the above build I can't reproduce the bug with the testcases and my dev website anymore. Can you confirm this? But with today's Nightly 56 x64 20170713100259 @ Debian Testing (Linux 4.11.0-1-amd64, Radeon RX480) it's still possible to reproduce. I don't know which changes happened between those two builds, but one or more fixed it.

(In reply to Darkspirit from comment #6) > (Darkspirit from bug 1380543 comment 7) > > Now I tried it with a try build from bug 1371450 comment 13: > > https://treeherder.mozilla.org/#/jobs?repo=try&revision=2deb83ce288532ce5f2b1534ffe6623b6ad9a9b2 > > > Linux x64 Stylo opt > tc[tier2] > B > target.tar.bz2 (stylo is enabled by default) > > With the above build I can't reproduce the bug with the testcases and my dev > website anymore. Can you confirm this? > > But with today's Nightly 56 x64 20170713100259 @ Debian Testing (Linux > 4.11.0-1-amd64, Radeon RX480) it's still possible to reproduce. I don't know > which changes happened between those two builds, but one or more fixed it. Thanks for the confirmation! You are right, I believe the try fixes this bug, actually I've been trying to fix this bug in that bug. :)

See comment 6 + comment 7: Fixed in try build from bug 1371450 comment 13.

Fixed in Nightly 56 x64 20170716100258 @ Debian Testing (Linux 4.11.0-1-amd64, Radeon RX480).