### 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

* **Electron Version:** 6.0.0-beta.13
* **Operating System:** Windows 12

### Expected Behavior

The documentation for the App events `browser-window-created` and `web-contents-created` state that the first parameter is an `Event`. I therefore expect the first parameter to be an `Event`.

### Actual Behavior

The first parameter for both of these events is `undefined`. (The second parameter is a `BrowserWindow` and `WebContents`, respectively, as documented.)
shell/browser/api/event_emitter.cc
v8::Local<v8::Object> object,
                                        v8::Local<v8::Object> custom_event) {
  v8::Local<v8::Object> event = CreateEventObject(isolate);
  (void)event->SetPrototype(custom_event->CreationContext(), custom_event);
  mate::Dictionary(isolate, event).Set("sender", object);
  return event;
}
v8::Local<v8::Object> CreateEventFromFlags(v8::Isolate* isolate, int flags) {
  const int mouse_button_flags =
      (ui::EF_RIGHT_MOUSE_BUTTON | ui::EF_LEFT_MOUSE_BUTTON |
       ui::EF_MIDDLE_MOUSE_BUTTON | ui::EF_BACK_MOUSE_BUTTON |
       ui::EF_FORWARD_MOUSE_BUTTON);
  const int is_mouse_click = static_cast<bool>(flags & mouse_button_flags);
  mate::Dictionary obj = mate::Dictionary::CreateEmpty(isolate);
  obj.Set("shiftKey", static_cast<bool>(flags & ui::EF_SHIFT_DOWN));
  obj.Set("ctrlKey", static_cast<bool>(flags & ui::EF_CONTROL_DOWN));
  obj.Set("altKey", static_cast<bool>(flags & ui::EF_ALT_DOWN));
  obj.Set("metaKey", static_cast<bool>(flags & ui::EF_COMMAND_DOWN));
  obj.Set("triggeredByAccelerator", !is_mouse_click);
  return obj.GetHandle();
}
}  
}