User Agent: Mozilla/5.0 (X11; Linux x86_64; rv:81.0) Gecko/20100101 Firefox/81.0

Steps to reproduce:

Since FF 81 tabs top line randomly becomes unresponsive to mouse clicks. On the latest nightly FF 82 too. Also this reproduces only on Linux, Windows version is fine.
Stable FF 80 has no such issue, so looks like a regression.
I've attached a video with the problem demonstration.

Bugbug thinks this bug should belong to this component, but please revert this change in case of error.

Could you help us find a regression range? https://mozilla.github.io/mozregression/

Regression bisection ended up here https://hg.mozilla.org/integration/autoland/pushloghtml?fromchange=483ef87aa6e85cb340d1c17b5b87bb7c217fb3b8&tochange=a4b38250348d81c88a2c21c9bcfb9f4ea4ca5c68

This is it https://hg.mozilla.org/integration/autoland/rev/6c7f2177e485c5eb00adb808e0356ac6b94f4400
And thats why the problem is Linux-only. Also when I'm starting FF with MOZ_USE_XINPUT2=0 env variable the problem disapears.

Thanks.

Dupe of Bug 1661219.

Although this was also caused my enabling XInput2, the actual symptoms are completely different from https://bugzilla.mozilla.org/show_bug.cgi?id=1661219, IMO this should stay open as the fix will likely be different.