d441aa82ae
Gnome introduced this in 2.30[0], Windows in 8[1].
Preview is just an "international prohibition symbol" to save the complicated
business of trying to calculate a semi-accurate one.
[0]
8eb0886312
https://bugzilla.gnome.org/show_bug.cgi?id=603551
[1]
https://superuser.com/questions/1061416/which-version-of-windows-introduced-the-span-wallpaper-style
Differential Revision: https://phabricator.services.mozilla.com/D23336