This code is too complicated to keep, and the last straw came after the
fixed width menu in the aggregate menu design.
This will break some existing popup menus that rely on the fixed width,
but this will soon be replaced with the aggregate menu. We'll also soon
clean this up further by replacing PopupBaseMenuItem's custom layout code
with an StBoxLayout.
https://bugzilla.gnome.org/show_bug.cgi?id=705845
c1fb1ba94c