wayland: Do not constrain saved window size

wayland: Do not constrain saved window size

Under Wayland, an xdg_surface.configure with size 0x0 means it's up to
the client to set its size.

When transitioning from maximized state to un-maximized, the Wayland
compositor will send such an 0x0 configure so that the client can
restore its original size.

However, the original size was already constrained, so re-applying
size constrains can lead to a smaller size when using size increments.

Avoid this caveat by not applying size constrains when we are restoring
the original size.

https://bugzilla.gnome.org/show_bug.cgi?id=777072