### 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
mate::Dictionary self(args->isolate(), args->GetThis());
  self.Set("defaultPrevented", true);
}
v8::Local<v8::Object> CreateEventObject(v8::Isolate* isolate) {
  if (event_template.IsEmpty()) {
    event_template.Reset(
        isolate,
        ObjectTemplateBuilder(isolate, v8::ObjectTemplate::New(isolate))
            .SetMethod("preventDefault", &PreventDefault)
            .Build());
  }
  return v8::Local<v8::ObjectTemplate>::New(isolate, event_template)
      ->NewInstance(isolate->GetCurrentContext())
      .ToLocalChecked();
}
}  
namespace internal {
v8::Local<v8::Object> CreateJSEvent(