code: private void updateStart(DownloadRequest request, long totalBytes) {
      /* if the request has failed before, donnot deliver callback */
      if (request.downloadState() == DownloadState.FAILURE) {
        updateState(request, DownloadState.RUNNING);
        return;
      }
  
      /* set the download state of this request as running */
      updateState(request, DownloadState.RUNNING);
      delivery.postStart(request, totalBytes);
    }
docs: /* update download start state