nsresult rv = NS_GetFileProtocolHandler(getter_AddRefs(fileHandler));
nsresult rv = NS_GetFileProtocolHandler(getter_AddRefs(fileHandler), ioService);
NS_GetURLSpecFromFile(nsIFile* aFile, nsACString &aUrl){    nsCOMPtr<nsIFileProtocolHandler> fileHandler;    nsresult rv = NS_GetFileProtocolHandler(getter_AddRefs(fileHandler));    if (NS_FAILED(rv)) return rv;    return fileHandler->GetURLSpecFromFile(aFile, aUrl);}