Can you file a bug asking for that kind of API event?

I saw similiar things requested...check this out:
https://bugzilla.mozilla.org/show_bug.cgi?id=1232178

EDITED 05.09.2017:
I followed your link and saw it was marked as resolved.

As I see in the 'linked' bug, they won't implement the functionality. They see WebExt have to deal with the web, not the browser chrome :\

This webextensions thing is getting tiresome...almost nothing will work (I mean extensions, from before)