Code review comment for lp:~alan-griffiths/mir/surface-states-simplification

This doesn't immediately *look* like a simplification to me.

My understanding is that this is a simplification for clients of this code - ie: consumers of this class no longer have to check if the EventSink or SurfaceID is set.

My question is then - do consumers of this class need to check if the EventSink or SurfaceID is set currently? It looks like consumers of this class generally won't care - if they configure() a surface which doesn't have an EventSink set then nothing will get the event but everything else will work as expected?