### 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 OpenURL(const std::string& url);
#if defined(OS_MACOSX)
  
  void NewWindowForTab();
#endif  
  
  
  void Activate(bool has_visible_windows);
  bool IsEmojiPanelSupported();
  
  void WillFinishLaunching();
  void DidFinishLaunching(base::DictionaryValue launch_info);
  void OnAccessibilitySupportChanged();
  void PreMainMessageLoopRun();
  
  
  void SetMainMessageLoopQuitClosure(base::OnceClosure quit_closure);
  void AddObserver(BrowserObserver* obs) { observers_.AddObserver(obs); }
  void RemoveObserver(BrowserObserver* obs) { observers_.RemoveObserver(obs); }
  bool is_shutting_down() const { return is_shutdown_; }
  bool is_quiting() const { return is_quiting_; }
  bool is_ready() const { return is_ready_; }
  v8::Local<v8::Value> WhenReady(v8::Isolate* isolate);
 protected:
  
  std::string GetExecutableFileVersion() const;
  
  std::string GetExecutableFileProductName() const;