Drupal 7 has drupal_goto() that would allow redirecting to an external url.
The change record indicated that ControllerBase::redirect is the method to be called in D8. https://www.drupal.org/node/2023537
This seems to work with internal drupal URLs but throws an error with external http urls -
[12-Nov-2014 21:00:22 Asia/Kolkata] Uncaught PHP Exception Symfony\Component\Routing\Exception\RouteNotFoundException: "Route "https://www.facebook.com/dialog/oaut....." does not exist." at /Applications/MAMP/htdocs/d8/core/lib/Drupal/Core/Routing/RouteProvider.php line 147
What would be the ideal equivalent of drupal_goto in D8 to redirect to an external URL?