### 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_win.cc
base::FilePath path;
  if (base::PathService::Get(base::FILE_EXE, &path)) {
    base::ThreadRestrictions::ScopedAllowIO allow_io;
    return FileVersionInfo::CreateFileVersionInfo(path);
  }
  return std::unique_ptr<FileVersionInfo>();
}
}  
Browser::UserTask::UserTask() = default;
Browser::UserTask::UserTask(const UserTask&) = default;
Browser::UserTask::~UserTask() = default;
void Browser::Focus() {
  
  DWORD pid = GetCurrentProcessId();
  EnumWindows(&WindowsEnumerationHandler, reinterpret_cast<LPARAM>(&pid));
}
void Browser::AddRecentDocument(const base::FilePath& path) {
  CComPtr<IShellItem> item;
  HRESULT hr = SHCreateItemFromParsingName(path.value().c_str(), NULL,
                                           IID_PPV_ARGS(&item));
  if (SUCCEEDED(hr)) {
    SHARDAPPIDINFO info;
    info.psi = item;
    info.pszAppID = GetAppUserModelID();
    SHAddToRecentDocs(SHARD_APPIDINFO, &info);
  }
}
void Browser::ClearRecentDocuments() {