### 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_linux.cc
const auto& opts = about_panel_options_;
  if (!opts.is_dict()) {
    LOG(WARNING) << "Called showAboutPanel(), but didn't use "
                    "setAboutPanelSettings() first";
    return;
  }
  GtkWidget* dialogWidget = gtk_about_dialog_new();
  GtkAboutDialog* dialog = GTK_ABOUT_DIALOG(dialogWidget);
  const std::string* str;
  const base::Value* val;
  if ((str = opts.FindStringKey("applicationName"))) {
    gtk_about_dialog_set_program_name(dialog, str->c_str());
  }
  if ((str = opts.FindStringKey("applicationVersion"))) {
    gtk_about_dialog_set_version(dialog, str->c_str());
  }
  if ((str = opts.FindStringKey("copyright"))) {
    gtk_about_dialog_set_copyright(dialog, str->c_str());
  }
  if ((str = opts.FindStringKey("website"))) {
    gtk_about_dialog_set_website(dialog, str->c_str());
  }
  if ((str = opts.FindStringKey("iconPath"))) {
    GError* error = nullptr;
    constexpr int width = 64;   
    constexpr int height = 64;  
    
    GdkPixbuf* icon =
        gdk_pixbuf_new_from_file_at_size(str->c_str(), width, height, &error);