- 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.h
#ifndef ATOM_BROWSER_API_ATOM_API_APP_H_
#define ATOM_BROWSER_API_ATOM_API_APP_H_
#include <string>
#include "atom/browser/api/event_emitter.h"
#include "atom/browser/atom_browser_client.h"
#include "atom/browser/browser_observer.h"
#include "atom/common/native_mate_converters/callback.h"
#include "chrome/browser/process_singleton.h"
#include "content/public/browser/gpu_data_manager_observer.h"
#include "native_mate/handle.h"
#include "net/base/completion_callback.h"
#if defined(USE_NSS_CERTS)
#include "chrome/browser/certificate_manager_model.h"
#endif
namespace base {
class FilePath;