6 files declare their use of AjaxResponseSubscriber in Zircon Profile 8

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

Contains \Drupal\Tests\Core\Ajax\AjaxResponseTest.

CommandsTest.php in core/modules/system/src/Tests/Ajax/CommandsTest.php

Contains \Drupal\system\Tests\Ajax\CommandsTest.

QuickEditIntegrationTest.php in core/modules/editor/src/Tests/QuickEditIntegrationTest.php

Contains \Drupal\editor\Tests\QuickEditIntegrationTest.

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

Contains \Drupal\views\Controller\ViewAjaxController.

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

Contains \Drupal\views_ui\ViewUI.

WebTestBase.php in core/modules/simpletest/src/WebTestBase.php

Contains \Drupal\simpletest\WebTestBase.