CONTEXT:
On rare sites, the Orca screen reader becomes completely unusable due to
the huge amount of events sent by Firefox. I don't reproduce the issue
on Windows with NVDA so I suspect the issue has been solved on Windows.

DESCRIPTION FROM UPSTREAM:
"Steps to reproduce:
1. Load the attached pyatspi accessible-event listener in a terminal
2. Load/reload matrix.org

Desired results: Not 450+ object:children-changed:add:system events for
images adding child images. :)

(I don't know if that's possible or not. But the act of examining these
events in Orca just to rule them out as event spam still takes more time
and a performance hit that is far from ideal. So if the spam could be
detected and fewer events emitted, I'd be grateful.)"