### Preflight Checklist

* [x] I have read the [Contributing Guidelines](https://github.com/electron/electron/blob/master/CONTRIBUTING.md) for this project.
* [x] I agree to follow the [Code of Conduct](https://github.com/electron/electron/blob/master/CODE_OF_CONDUCT.md) that this project adheres to.
* [x] I have searched the issue tracker for an issue that matches the one I want to file, without success.

### Issue Details

It would appear that `app.focus()` stopped working in Electron 6, and remains broken in Electron 8.

* **Electron Version:**
  * 8.0.3
* **Operating System:**
  * macOS
* **Last Known Working Electron version:**
  * 5.0.13

### Expected Behavior
`app.focus()` should bring the application to the foreground.

### Actual Behavior
`app.focus()` does nothing.

### To Reproduce

Fiddle: https://gist.github.com/a772265b312329e3f3bc1feb7b6aff7d

1) Start this fiddle.
2) As soon as the window pops up, select another application so that Electron is in the background.
3) Within 5 seconds, the app will attempt to focus itself to no avail.

shell/browser/browser.h
void NotifyAndShutdown();
  
  bool HandleBeforeQuit();
  bool is_quiting_ = false;
 private:
  
  void OnWindowCloseCancelled(NativeWindow* window) override;
  void OnWindowAllClosed() override;
  
  base::ObserverList<BrowserObserver> observers_;
  
  bool is_exiting_ = false;
  
  bool is_ready_ = false;
  
  bool is_shutdown_ = false;
  
  base::OnceClosure quit_main_message_loop_;
  int badge_count_ = 0;
  std::unique_ptr<gin_helper::Promise<void>> ready_promise_;
#if defined(OS_LINUX) || defined(OS_WIN)
  base::Value about_panel_options_;
#elif defined(OS_MACOSX)
  base::DictionaryValue about_panel_options_;
#endif
  DISALLOW_COPY_AND_ASSIGN(Browser);
};
}  
#endif