What purpose has this class? It looks like it tries to decouple Clients of this class (things that need something layed out) from the actual implementation (RowLayout). But since it Layout depends on RowLayout that coupling actually does not happen. Or to put it the other way round: If you want to add a layout implementation, this class has to change. 

If actually want to achieve decoupling, Layout should be an interface implemented by RowLayout. But since there is currently only a single implementation, one could use Layout completely for now.