### 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
}
namespace gin_helper {
class Arguments;
}
namespace electron {
class ElectronMenuModel;
class Browser : public WindowListObserver {
 public:
  Browser();
  ~Browser() override;
  static Browser* Get();
  
  void Quit();
  
  void Exit(gin_helper::Arguments* args);
  
  void Shutdown();
  
  void Focus();
  
  std::string GetVersion() const;
  
  void SetVersion(const std::string& version);
  
  std::string GetName() const;
  
  void SetName(const std::string& name);