### 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 SetLoginItemSettings(LoginItemSettings settings);
  LoginItemSettings GetLoginItemSettings(const LoginItemSettings& options);
#if defined(OS_MACOSX)
  
  void SetShutdownHandler(base::Callback<bool()> handler);
  
  void Hide();
  
  void Show();
  
  void SetUserActivity(const std::string& type,
                       base::DictionaryValue user_info,
                       gin_helper::Arguments* args);
  
  std::string GetCurrentActivityType();
  
  
  void InvalidateCurrentActivity();
  
  void ResignCurrentActivity();
  
  void UpdateCurrentActivity(const std::string& type,
                             base::DictionaryValue user_info);
  
  bool WillContinueUserActivity(const std::string& type);
  
  void DidFailToContinueUserActivity(const std::string& type,
                                     const std::string& error);