15 files declare their use of WebformCompositeBase in Webform 8.5

EmailWebformHandler.php in src/Plugin/WebformHandler/EmailWebformHandler.php

RemotePostWebformHandler.php in src/Plugin/WebformHandler/RemotePostWebformHandler.php

WebformDevelSchema.php in modules/webform_devel/src/WebformDevelSchema.php

WebformElementBase.php in src/Plugin/WebformElementBase.php

WebformElementComposite.php in src/Element/WebformElementComposite.php

WebformElementHelper.php in src/Utility/WebformElementHelper.php

WebformExampleComposite.php in modules/webform_example_composite/src/Plugin/WebformElement/WebformExampleComposite.php

WebformSubmissionConditionsValidator.php in src/WebformSubmissionConditionsValidator.php

WebformSubmissionExportImportImporter.php in modules/webform_submission_export_import/src/WebformSubmissionExportImportImporter.php

WebformSubmissionForm.php in src/WebformSubmissionForm.php

WebformTestComposite.php in tests/modules/webform_test_element/src/Plugin/WebformElement/WebformTestComposite.php

WebformTestCompositeFile.php in tests/modules/webform_test_element/src/Plugin/WebformElement/WebformTestCompositeFile.php

WebformTranslationManager.php in src/WebformTranslationManager.php

webform_test.test_element_help_display.inc in tests/modules/webform_test/includes/webform_test.test_element_help_display.inc

Generate test elements help displays.

webform_test.test_element_title_display.inc in tests/modules/webform_test/includes/webform_test.test_element_title_display.inc

Generate test elements title displays.