It's going to be removed from Chromium, see https://crbug.com/812523.

/cc @electron/code-owners 
chromium_src/chrome/browser/certificate_manager_model.cc
net::NSSCertDatabase* cert_db,
    bool is_user_db_available,
    const CreationCallback& callback) {
  DCHECK_CURRENTLY_ON(BrowserThread::UI);
  std::unique_ptr<CertificateManagerModel> model(
      new CertificateManagerModel(cert_db, is_user_db_available));
  callback.Run(std::move(model));
}
void CertificateManagerModel::DidGetCertDBOnIOThread(
    const CreationCallback& callback,
    net::NSSCertDatabase* cert_db) {
  DCHECK_CURRENTLY_ON(BrowserThread::IO);
  bool is_user_db_available = !!cert_db->GetPublicSlot();
  base::PostTask(
      FROM_HERE, {BrowserThread::UI},
      base::BindOnce(&CertificateManagerModel::DidGetCertDBOnUIThread, cert_db,
                     is_user_db_available, callback));
}
void CertificateManagerModel::GetCertDBOnIOThread(
    content::ResourceContext* context,
    const CreationCallback& callback) {
  DCHECK_CURRENTLY_ON(BrowserThread::IO);
  net::NSSCertDatabase* cert_db = GetNSSCertDatabaseForResourceContext(
      context, base::BindOnce(&CertificateManagerModel::DidGetCertDBOnIOThread,
                              callback));
  if (cert_db)
    DidGetCertDBOnIOThread(callback, cert_db);
}