10 files declare their use of LanguageNegotiationMethodBase in Drupal 8

LanguageNegotiationBrowser.php in core/modules/language/src/Plugin/LanguageNegotiation/LanguageNegotiationBrowser.php

LanguageNegotiationContentEntity.php in core/modules/language/src/Plugin/LanguageNegotiation/LanguageNegotiationContentEntity.php

LanguageNegotiationSelected.php in core/modules/language/src/Plugin/LanguageNegotiation/LanguageNegotiationSelected.php

LanguageNegotiationSession.php in core/modules/language/src/Plugin/LanguageNegotiation/LanguageNegotiationSession.php

LanguageNegotiationTest.php in core/modules/language/tests/language_test/src/Plugin/LanguageNegotiation/LanguageNegotiationTest.php

LanguageNegotiationUI.php in core/modules/language/src/Plugin/LanguageNegotiation/LanguageNegotiationUI.php

LanguageNegotiationUrl.php in core/modules/language/src/Plugin/LanguageNegotiation/LanguageNegotiationUrl.php

LanguageNegotiationUrlFallback.php in core/modules/language/src/Plugin/LanguageNegotiation/LanguageNegotiationUrlFallback.php

LanguageNegotiationUser.php in core/modules/user/src/Plugin/LanguageNegotiation/LanguageNegotiationUser.php

LanguageNegotiationUserAdmin.php in core/modules/user/src/Plugin/LanguageNegotiation/LanguageNegotiationUserAdmin.php