- 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
#include "atom/browser/api/atom_api_app.h"
#include <string>
#include <vector>
#include "atom/browser/api/atom_api_menu.h"
#include "atom/browser/api/atom_api_session.h"
#include "atom/browser/api/atom_api_web_contents.h"
#include "atom/browser/atom_browser_context.h"
#include "atom/browser/atom_browser_main_parts.h"
#include "atom/browser/browser.h"
#include "atom/browser/login_handler.h"
#include "atom/common/native_mate_converters/callback.h"
#include "atom/common/native_mate_converters/file_path_converter.h"
#include "atom/common/native_mate_converters/gurl_converter.h"
#include "atom/common/native_mate_converters/image_converter.h"