11 files declare their use of FlagServiceInterface in Flag 8.4

ActionLinkController.php in src/Controller/ActionLinkController.php

ActionLinkNoJsController.php in src/Controller/ActionLinkNoJsController.php

EntityFlagActionDeriver.php in src/Plugin/Derivative/EntityFlagActionDeriver.php

FlagAccessCheck.php in src/Access/FlagAccessCheck.php

FlagAction.php in src/Plugin/Action/FlagAction.php

FlagActionTest.php in tests/src/Unit/Plugin/Action/FlagActionTest.php

FlagEvents.php in tests/modules/flag_event_test/src/EventSubscriber/FlagEvents.php

FlagPermissions.php in src/Permissions/FlagPermissions.php

FlagResetForm.php in src/Form/FlagResetForm.php

FlagViewsRelationship.php in src/Plugin/views/relationship/FlagViewsRelationship.php

UnFlagAccessCheck.php in src/Access/UnFlagAccessCheck.php