Enables "credentials mode" for this XHR request. Disabled by default.

"Credentials mode" causes cookies and other credentials to be sent and received. It has complicated implications for CORS headers required from the server.

Example

Future<void> main() async {
  final client = HttpClient();
  final request = client.getUrl(Url.parse('http://host/path'));
  if (request is BrowserHttpClientRequest) {
    request.browserCredentialsMode = true;
  }
  final response = await request.close();
  // ...
}