In a HiDPI environment, all gtk+ apps will report a 2 x 2 size
increment to avoid odd size. But that does not mean they are
resizing in cells like terminals, so they resize popup should
not be shown.

Ideally, we should ignore <= scale x scale increments, but in
practice scale is 1 or 2, and even in a lo-dpi setting a 2 x 2
increment makes little sense so let's keep the patch simple.