Both the position and size of the frame actor depend on the scale
of the workspace, so update them both when the scale changes.
On the other hand, the the frame actor doesn't need to be
repositioned when the workspace moves (since it is relative to the
workspace). We do base the frame position of the desktop actor, but
that will presumably stay fixed (at 0,0) in most all cases.
http://bugzilla.gnome.org/show_bug.cgi?id=591122
02ee6f69b3