In the new mockups, the user menu icons are on the right, not the
left.
Also, get rid of the idea of optional icons; the design doesn't have
icons on those items, and there probably aren't going to be symbolic
versions of some of those icons anyway. So if the caller specifies
PopupImageMenuItem, then always show an icon, and just use regular
PopupMenuItems for the items that don't have icons in the current
design.
https://bugzilla.gnome.org/show_bug.cgi?id=631193
86efdc906a