Enables CORS "credentials mode" for all XHR requests. 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();
  if (client is BrowserHttpClient) {
    client.browserCredentialsMode = true;
  }
  // ...
}