8 files declare their use of SqlEntityStorageInterface in Drupal 8

content_translation.install in core/modules/content_translation/content_translation.install

Installation functions for Content Translation module.

EntityViewsData.php in core/modules/views/src/EntityViewsData.php

KernelTestBase.php in core/tests/Drupal/KernelTests/KernelTestBase.php

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

media.install in core/modules/media/media.install

Install, uninstall and update hooks for Media module.

Tables.php in core/lib/Drupal/Core/Entity/Query/Sql/Tables.php

taxonomy.install in core/modules/taxonomy/taxonomy.install

Install, update and uninstall functions for the taxonomy module.

views_test_query_access.module in core/modules/views/tests/modules/views_test_query_access/views_test_query_access.module

Module to test entity query access in Views.