nsresult CStreamListener::QueryInterface(const nsIID& aIID, void** aInstancePtr) { return NS_ERROR_NOT_IMPLEMENTED; }
NS_IMPL_ISUPPORTS(RobotSinkObserver, kIRobotSinkObserverIID);
nsresult CStreamListener::QueryInterface(const nsIID& aIID, void** aInstancePtr)  {                                                                          return NS_ERROR_NOT_IMPLEMENTED;      // never called}