10 files declare their use of FeaturesBundleInterface in Features 8.4

AssignmentConfigureForm.php in modules/features_ui/src/Form/AssignmentConfigureForm.php

features.drush8.inc in drush/features.drush8.inc

Features module drush integration.

FeaturesBundle.php in src/Entity/FeaturesBundle.php

FeaturesBundleIntegrationTest.php in tests/src/Kernel/Entity/FeaturesBundleIntegrationTest.php

FeaturesBundleUiTest.php in modules/features_ui/tests/src/Functional/FeaturesBundleUiTest.php

FeaturesCommands.php in src/Commands/FeaturesCommands.php

FeaturesExportForm.php in modules/features_ui/src/Form/FeaturesExportForm.php

FeaturesGenerationArchive.php in src/Plugin/FeaturesGeneration/FeaturesGenerationArchive.php

FeaturesGenerationWrite.php in src/Plugin/FeaturesGeneration/FeaturesGenerationWrite.php

FeaturesManagerTest.php in tests/src/Unit/FeaturesManagerTest.php