When we skip calling SampleAnimations() we should clear mPreviousTimeStamp, otherwise we will use the timestamp that is far behind from the timestamp on the main-thread, that leads visual gaps for animations. This change should fix failures that happened when the patches for bug 1456679 landed. A try with patches for bug 1456679 and bug 1458457. https://treeherder.mozilla.org/#/jobs?repo=try&revision=6868cfe1c27e577106084fbb6b5ec10483a98a77 And here is a try only with the patch for this bug. https://treeherder.mozilla.org/#/jobs?repo=try&revision=444751fca3735a0098a2a4fbf3fe46f6f4fefa54

Comment on attachment 8972782 [details] Bug 1458798 - Clear the previous timestamp when we skip calling SampleAnimations in CompositeToTarget(). https://reviewboard.mozilla.org/r/241346/#review247210 I don't really like that this is duplicated and separated from the rest of the code in AdvanceAnimations(), but I can't think of a better way to structure it to, so r+. We can always change it later if we find a better way to do this.

Pushed by kgupta@mozilla.com: https://hg.mozilla.org/integration/autoland/rev/da163bfbc6c8 Clear the previous timestamp when we skip calling SampleAnimations in CompositeToTarget(). r=kats