window: Always sync window geometry on state change

When a state changed, e.g. a window went from unfullscreen to
fullscreen, always sync the window geometry, otherwise a compositor
application (e.g. gnome-shell) might end up with an unfinished window
state transition effect.

Without always syncing, the compositor plugin will see a 'size-change'
event, as a result of the state change, but if the size didn't change,
it would never see the 'size-changed' event. If an effect, for example
gnome-shell's fullscreen effect, is triggered on 'size-change' it might
rely on the actual size change to not get stuck. This commit allows it
to have this dependency.

This fixes a bug where a fullscreen effect gets "stuck" when a window
goes fullscreen without changing the window geometry.

https://bugzilla.gnome.org/show_bug.cgi?id=780292