### 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
bool ContinueUserActivity(const std::string& type,
                            base::DictionaryValue user_info);
  
  void UserActivityWasContinued(const std::string& type,
                                base::DictionaryValue user_info);
  
  bool UpdateUserActivityState(const std::string& type,
                               base::DictionaryValue user_info);
  
  enum class BounceType{
      CRITICAL = 0,        
      INFORMATIONAL = 10,  
  };
  int DockBounce(BounceType type);
  void DockCancelBounce(int request_id);
  
  void DockDownloadFinished(const std::string& filePath);
  
  void DockSetBadgeText(const std::string& label);
  std::string DockGetBadgeText();
  
  void DockHide();
  v8::Local<v8::Promise> DockShow(v8::Isolate* isolate);
  bool DockIsVisible();
  
  void DockSetMenu(ElectronMenuModel* model);
  
  void DockSetIcon(const gfx::Image& image);
#endif  
  void ShowAboutPanel();