6 files declare their use of CloseDialogCommand in Drupal 8

AddFormBase.php in core/modules/media_library/src/Form/AddFormBase.php

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

AjaxTestController.php in core/modules/system/tests/modules/ajax_test/src/Controller/AjaxTestController.php

ContentModerationConfigureEntityTypesForm.php in core/modules/content_moderation/src/Form/ContentModerationConfigureEntityTypesForm.php

LayoutRebuildTrait.php in core/modules/layout_builder/src/Controller/LayoutRebuildTrait.php

MediaLibrarySelectForm.php in core/modules/media_library/src/Plugin/views/field/MediaLibrarySelectForm.php