MessengerSaver
fDocument->SetNativeSaver(new MessengerSaver(externalObserver));
MessengerSaver::MessengerSaver(const BMessenger& messenger)
MessengerSaver::~MessengerSaver()
MessengerSaver::Save(Document* document)
class MessengerSaver : public DocumentSaver {
MessengerSaver(const BMessenger& messenger);
virtual ~MessengerSaver();