code executed in wrong order with setTimeout after alert

[goooooouwa]

This is a bug I found a year ago, I reported it in Bugzilla (https://bugzilla.mozilla.org/show_bug.cgi?id=1167575) with no fix even today. It can still be reproduced in the latest release Firefox(48.0.1) and nighty build Firefox Nightly 51.0a1(2016-08-24).
I'm posting it here to get help on the bug fixing, since it's taking too long there. Any suggestion that would help us resolve this bug is appreciated.