Tor Browser and Unsafe Browser have no minimize & maximize buttons in the window titlebar

Regression in 5.8 (wb:b841a57a2e3b3d4752a73c974a75e3c5). I suppose that's because we run them as native Wayland apps, so they're responsible for CSD (client-side decoration).

It looks like Firefox tries to honor the system config regarding titlebar content:

• https://bugzilla.mozilla.org/show_bug.cgi?id=1432090
• git grep -E 'button-layout|gtk-decoration-layout' in the Firefox Git repo

Could it be that we block its access to said system config?

User research findings

• This issue has been pretty loud on our Help Desk since it 5.8.

• During #18648 (closed), 3 out of 4 participants wanted to minimize Tor Browser and complained about the lack of minimize button. None of them found the workaround.

Workaround

Both operations are accessible from the window list.