Comment 9 for bug 1152854

gtk-window-decorator uses libmetacity in order to load themes. If it cant handle a theme, its libmetacity's problem, and probably a problem with the version we ship in ubuntu.

(Note, gtk-window-decorator won't be ported to use libmutter. Substantial API required in order to use it has been removed from libmutter, and it would also require that gtk-window-decorator would be ported to use the gtk+3.0 api, something which is not a trivial task because we're quite heavily dependent on the GdkX11 stuff).