call-window: use GTK_STYLE_CLASS_OSD for the floating toolbar
call-window: use GTK_STYLE_CLASS_OSD for the floating toolbar

https://bugzilla.gnome.org/show_bug.cgi?id=676569

GNOME/telepathy-account-widgets,Distrotech/telepathy-account-widgets,GNOME/telepathy-account-widgets,Distrotech/telepathy-account-widgets,GNOME/telepathy-account-widgets