9 files declare their use of ResponsiveImageStyle in Drupal 8

ResponsiveImageFieldDisplayTest.php in core/modules/responsive_image/tests/src/Functional/ResponsiveImageFieldDisplayTest.php

ResponsiveImageFieldUiTest.php in core/modules/responsive_image/src/FunctionalJavascript/ResponsiveImageFieldUiTest.php

ResponsiveImageFormatter.php in core/modules/responsive_image/src/Plugin/Field/FieldFormatter/ResponsiveImageFormatter.php

ResponsiveImageIntegrationTest.php in core/modules/responsive_image/tests/src/Kernel/ResponsiveImageIntegrationTest.php

ResponsiveImageStyleConfigEntityUnitTest.php in core/modules/responsive_image/tests/src/Unit/ResponsiveImageStyleConfigEntityUnitTest.php

ResponsiveImageStyleResourceTestBase.php in core/modules/responsive_image/tests/src/Functional/Rest/ResponsiveImageStyleResourceTestBase.php

ResponsiveImageStyleTest.php in core/modules/jsonapi/tests/src/Functional/ResponsiveImageStyleTest.php

responsive_image.module in core/modules/responsive_image/responsive_image.module

Responsive image display formatter for image fields.

ViewsIntegrationTest.php in core/modules/responsive_image/tests/src/Functional/ViewsIntegrationTest.php