6 files declare their use of CacheableJsonResponse

ExceptionHandlingTest.php in core/tests/Drupal/KernelTests/Core/Routing/ExceptionHandlingTest.php
ExceptionJsonSubscriber.php in core/lib/Drupal/Core/EventSubscriber/ExceptionJsonSubscriber.php
ExceptionJsonSubscriberTest.php in core/tests/Drupal/Tests/Core/EventSubscriber/ExceptionJsonSubscriberTest.php
JsonRenderer.php in core/modules/system/tests/modules/common_test/src/Render/MainContent/JsonRenderer.php
LinksetController.php in core/modules/system/src/Controller/LinksetController.php
PageCacheAcceptHeaderController.php in core/modules/system/tests/modules/system_test/src/Controller/PageCacheAcceptHeaderController.php

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