* @param internalApi The driver for the GWT collaborative libraries.
* @param errorHandler The third-party error handling function.
*/
DocumentImpl(final DocumentBridge internalApi, final Handler<Error> errorHandler) {
model = new ModelImpl(internalApi, this);
handlerRegs = new Registrations();
collaborators = Json.createObject();
Bus bus = internalApi.store.getBus();
if (errorHandler != null) {
handlerRegs.wrap(bus.subscribeLocal(