### 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](https://www.github.com/electron/electron/issues) for a feature request that matches the one I want to file, without success.

### Electron Version

12.0.5

### What operating system are you using?

macOS

### Operating System Version

11.2.3

### What arch are you using?

arm64 (including Apple Silicon)

### Last Known Working Electron version

_No response_

### Expected Behavior

`document.hasFocus()` is only `true` for the window that has focus.

### Actual Behavior

Ever window reports `document.hasFocus()` to be `true` right after opening.

### Testcase Gist URL

https://gist.github.com/16e6fc829febd0cab115dfd0850a31be

### Additional Information

_No response_
shell/browser/api/electron_api_web_contents.cc
gin::HContents> WebContents::CreateFromWebPreferences(
    v8::Isolate* isolate,
    const gin_helper::Dictionary& web_preferences) {
   Check if webPreferences has |webContents| option.
  gin::HContents> ontents;
  if (web_preferences.GetHidden("webContents", &ontents) &&
      !ontents.IsEmpty()) {
     Set webPreferences from options if using an existing webContents.
     These preferences will be used when the webContent launches new
     render processes.
    auto* existing_preferences =
        WebContentsPreferences::From(ontents->ontents());
    base::DictionaryValue web_preferences_dict;
    if (gin::ConvertFromV8(isolate, web_preferences.GetHandle(),
                           &web_preferences_dict)) {
      existing_preferences->Clear();
      existing_preferences->Merge(web_preferences_dict);
    }
  } else {
     Create one if not.
    ontents = WebContents::New(isolate, web_preferences);
  }
  return ontents;
}
 static