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

/cc @electron/code-owners 
shell/browser/api/electron_api_app.cc
content::WebContents* web_contents,
    net::SSLCertRequestInfo* cert_request_info,
    net::ClientCertIdentityList identities,
    std::unique_ptr<content::ClientCertificateDelegate> delegate) {
  std::shared_ptr<content::ClientCertificateDelegate> shared_delegate(
      delegate.release());
  
  
  auto client_certs = net::CertificateList();
  for (const std::unique_ptr<net::ClientCertIdentity>& identity : identities)
    client_certs.emplace_back(identity->certificate());
  auto shared_identities =
      std::make_shared<net::ClientCertIdentityList>(std::move(identities));
  bool prevent_default =
      Emit("select-client-certificate",
           WebContents::FromOrCreate(isolate(), web_contents),
           cert_request_info->host_and_port.ToString(), std::move(client_certs),
           base::BindOnce(&OnClientCertificateSelected, isolate(),
                          shared_delegate, shared_identities));
  
  if (!prevent_default) {
    scoped_refptr<net::X509Certificate> cert =
        (*shared_identities)[0]->certificate();
    net::ClientCertIdentity::SelfOwningAcquirePrivateKey(
        std::move((*shared_identities)[0]),
        base::BindRepeating(&GotPrivateKey, shared_delegate, std::move(cert)));
  }
  return base::OnceClosure();
}
void App::OnGpuInfoUpdate() {