Comment 21 for bug 1625846

(The reason why bug 1671771 is not going to fix this is that Firefox¹ *may* set input focus to one of its subwindows, and will behave weirdly if that doesn't work. You can't just set “no focus” on the Mir surface corresponding to Firefox's subwindow and then delegate to Mir's input focus.)

¹: And, if not Firefox, then there'll definitely be *some* X11 app which does this ☺