User Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/86.0.4240.183 Safari/537.36

Steps to reproduce:

https://jsfiddle.net/snowystinger/ceta7fqo/23/
Follow steps outlined in fiddle.

Actual results:

Text selection starts after clicking Foo and this is the console output.
Foo:
foo pointerup capture
body got pointerup

Bar:
bar pointerup capture
body got pointerup
bar mouseup capture
body got mouseup

Expected results:

Foo:
foo pointerup capture
body got pointerup
body got mouseup

This is what happens in Chrome, there is no text selection and all events are fired.
Bar:
bar pointerup capture
body got pointerup
bar mouseup capture
body got mouseup

Regression window:
https://hg.mozilla.org/integration/mozilla-inbound/pushloghtml?fromchange=ec28a490365c49cfd4320648652441e1ad8e779f&tochange=2155af8d88c3bd116305378d7e22b947db339c55

Edgar, would you have time to take a look at this?

I will take a look after the fission focus work.

It looks like we need to do the hittest again after dispatching pointer event if the target is removed in pointer event handler.