How do I redirect to an external URL? 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?
With a route name on a Controller:

use Drupal\Core\Controller\ControllerBase;

class MyControllerClass extends ControllerBase {

  public function foo() {
    //...
    return $this-&gt;redirect('user.page');
  }
}


With an absolute URL:

return new RedirectResponse('https://google.com');


On a form RedirectResponse doesn't work, then:

With a route name:

public function submitForm(array &amp;$form, FormStateInterface $form_state) {
  //...

  $form_state-&gt;setRedirect('user.page');
}


With an absolute URL:

public function submitForm(array &amp;$form, FormStateInterface $form_state) {
  //...

  $form_state-&gt;setResponse(new TrustedRedirectResponse('https://google.com', 302));
  // You can change the response code from 302 to whatever you need
}