cogl: Compensate for window scaling
cogl: Compensate for window scaling

The common stage window code that we share on Cogl-based backends should
also use the scaling factor.

https://bugzilla.gnome.org/show_bug.cgi?id=705915

djdeath/clutter,Distrotech/clutter,Distrotech/clutter,ebassi/clutter,ebassi/clutter,djdeath/clutter,Distrotech/clutter,jigpu/clutter,ebassi/clutter,ebassi/clutter,GNOME/clutter,jigpu/clutter,GNOME/clutter,djdeath/clutter,Distrotech/clutter,Distrotech/clutter,GNOME/clutter,jigpu/clutter,jigpu/clutter,ebassi/clutter,jigpu/clutter,djdeath/clutter,GNOME/clutter,Distrotech/clutter,GNOME/clutter,jigpu/clutter,djdeath/clutter,djdeath/clutter