This supplier regulate macro recording of XDispatch::dispatch()
calls. For that it capsulate a reference to a DispatchRecorder.
Such recorder is used internaly and can be used externaly too.
A supplier will be available on a Frame if recording was enabled,
otherwise not. A frame supports a special property for that.
This modular concept of recorder, supplier and frame makes it possible to
implement local recording on one frame; global recording by using all currently
opened frames or only some of them; and so on.
