- Electron version: 1.1.0
- Operating system: Windows
- Use case: cleanup and reporting tasks executed on quit (headless), which may take time and should not prevent from opening a new instance.
- Proposed solutions:
  - new _app.releaseSingleInstance()_ API which free the singleInstance lock
  - replace _app.releaseSingleInstance()_ API by an event listener (which may be listened/unlistened)
  - [app.makeSingleInstance](https://github.com/electron/electron/blob/master/docs/api/app.md#appmakesingleinstancecallback) returns the result of the callback function. So we can choose to quit or not in a more accurate way.
  - Provide a communication channel between the new instance and the main one (in callback arguments)

atom/browser/api/atom_api_app.cc
content::WebContents* web_contents,
    net::SSLCertRequestInfo* cert_request_info,
    std::unique_ptr<content::ClientCertificateDelegate> delegate) {
  std::shared_ptr<content::ClientCertificateDelegate>
      shared_delegate(delegate.release());
  bool prevent_default =
      Emit("select-client-certificate",
           WebContents::CreateFrom(isolate(), web_contents),
           cert_request_info->host_and_port.ToString(),
           cert_request_info->client_certs,
           base::Bind(&OnClientCertificateSelected,
                      isolate(),
                      shared_delegate));
  
  if (!prevent_default)
    shared_delegate->ContinueWithCertificate(
        cert_request_info->client_certs[0].get());
}
void App::OnGpuProcessCrashed(base::TerminationStatus exit_code) {