it: test dnd focus change on drop

src/it/test_transport.rs

@@ -61,6 +61,7 @@ impl TestTransport {
             xdg: Default::default(),
             activation: Default::default(),
             foreign_toplevel_list: Default::default(),
+            data_device_manager: Default::default(),
             seats: Default::default(),
         });
         self.send(wl_display::GetRegistry {