ArStateChangeRegistrar

data class ArStateChangeRegistrar

Used to register Ar status changes via PublishSubject.

oldState - the old ArState

newState - the new ArState.

ArStateChangeRegistrar(oldState: ArState, newState: ArState)

Used to register Ar status changes via PublishSubject.

newState	`val newState: ArState` the new ArState.
oldState	`val oldState: ArState` the old ArState