### 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
#ifndef SHELL_BROWSER_BROWSER_H_
#define SHELL_BROWSER_BROWSER_H_
#include <memory>
#include <string>
#include <vector>
#include "base/compiler_specific.h"
#include "base/macros.h"
#include "base/observer_list.h"
#include "base/strings/string16.h"
#include "base/values.h"
#include "shell/browser/browser_observer.h"
#include "shell/browser/window_list_observer.h"
#include "shell/common/gin_helper/promise.h"
#if defined(OS_WIN)
#include <windows.h>
#include "base/files/file_path.h"
#endif
namespace base {
class FilePath;
}
namespace gfx {
class Image;