7 files declare their use of CachePluginBase in Drupal 9

DisplayKernelTest.php in core/modules/views/tests/src/Kernel/Plugin/DisplayKernelTest.php

media_library.module in core/modules/media_library/media_library.module

Contains hook implementations for the media_library module.

test_basetheme.theme in core/modules/system/tests/themes/test_basetheme/test_basetheme.theme

Add hooks for tests to use.

test_subtheme.theme in core/modules/system/tests/themes/test_subtheme/test_subtheme.theme

Add hooks for tests to use.

ViewExecutableTest.php in core/modules/views/tests/src/Unit/ViewExecutableTest.php

views.api.php in core/modules/views/views.api.php

Describes hooks and plugins provided by the Views module.

views_test_data.views_execution.inc in core/modules/views/tests/modules/views_test_data/views_test_data.views_execution.inc

Provides views data and hooks for views_test_data module.