assignJob method
Registers job as the handler invoked for every message emitted by this
service.
job receives a non-null Pointer<BackendMsg>. freeMessage is called
automatically once job returns.
Implementation
@nonVirtual
void assignJob(void Function(Pointer<BackendMsg>) job) {
messageStream.listen((message) {
job(message);
freeMessage(message);
});
}