6 files declare their use of QueueWorkerBase in Drupal 8

AggregatorRefresh.php in core/modules/aggregator/src/Plugin/QueueWorker/AggregatorRefresh.php

CronQueueTestBrokenQueue.php in core/modules/system/tests/modules/cron_queue_test/src/Plugin/QueueWorker/CronQueueTestBrokenQueue.php

CronQueueTestException.php in core/modules/system/tests/modules/cron_queue_test/src/Plugin/QueueWorker/CronQueueTestException.php

CronQueueTestRequeueException.php in core/modules/system/tests/modules/cron_queue_test/src/Plugin/QueueWorker/CronQueueTestRequeueException.php

LocaleTranslation.php in core/modules/locale/src/Plugin/QueueWorker/LocaleTranslation.php

ThumbnailDownloader.php in core/modules/media/src/Plugin/QueueWorker/ThumbnailDownloader.php