6 files declare their use of ReplaceCommand in Zircon Profile 8

AjaxCommandsTest.php in core/tests/Drupal/Tests/Core/Ajax/AjaxCommandsTest.php

Contains \Drupal\Tests\Core\Ajax\AjaxCommandsTest.

FormAjaxSubscriber.php in core/lib/Drupal/Core/Form/EventSubscriber/FormAjaxSubscriber.php

Contains \Drupal\Core\Form\EventSubscriber\FormAjaxSubscriber.

ManagedFile.php in core/modules/file/src/Element/ManagedFile.php

Contains \Drupal\file\Element\ManagedFile.

ViewAjaxController.php in core/modules/views/src/Controller/ViewAjaxController.php

Contains \Drupal\views\Controller\ViewAjaxController.

ViewEditForm.php in core/modules/views_ui/src/ViewEditForm.php

Contains \Drupal\views_ui\ViewEditForm.

ViewsUIController.php in core/modules/views_ui/src/Controller/ViewsUIController.php

Contains \Drupal\views_ui\Controller\ViewsUIController.