Replace $form_state['redirect_route'] with setRedirect()

Can we change the scope of the issue to Add FormState::setRedirect()?

So perhaps replace $form_state['redirect'] and $form_state['redirect_route'] with setRedirect(\Drupal\Core\Url $url);. I think it will include conversion in it.

I like this apporoch. Are these all the redirect we have in the core?
Minor doc improvement suggestions.

1. +++ b/core/lib/Drupal/Core/Form/FormStateInterface.php
   @@ -75,6 +75,23 @@ public function setFormState(array $form_state_additions);
   +   * @see \Drupal\Core\Form\FormSubmitterInterface::redirectForm()
   

   I think we should also add @see setRedirectUrl here.

2. +++ b/core/lib/Drupal/Core/Form/FormStateInterface.php
   @@ -84,7 +101,7 @@ public function setIfNotExists($property, $value);
       * @see \Drupal\Core\Form\FormSubmitterInterface::redirectForm()
   

   I think we should also add @see setRedirect here.

Yep, that's exactly what I meant, nice.

Thank you for the reroll. This is RTBC. Needs change notice update and a follow up for path-based redirects.

This is looking good.

FormState::getRedirect() has the following code / comment:

    if ($redirect_route = $this->get('redirect_route')) {
      // @todo Remove once all redirects are converted to \Drupal\Core\Url. See
      //   https://www.drupal.org/node/2189661.
      if (!($redirect_route instanceof Url)) {
        $redirect_route += array(
          'route_parameters' => array(),
          'options' => array(),
        );
        $redirect_route = new Url($redirect_route['route_name'], $redirect_route['route_parameters'], $redirect_route['options']);
      }

      $redirect_route->setAbsolute();
      return $redirect_route;
    }

At the very least the @todo needs updating to point to a new issue.

@jibran re #22 can you list the CRs you think need updating. Thanks.

#24 is addressed so back to RTBC.
re #25 https://www.drupal.org/node/2189619 and https://www.drupal.org/node/2174429

Committed 627a719 and pushed to 8.0.x. Thanks!

Thank you @alexpott for the commit. I have updated the change notices.