10 files declare their use of LanguageNegotiationUrl in Zircon Profile 8

EntityUrlLanguageTest.php in core/modules/language/src/Tests/EntityUrlLanguageTest.php

Contains \Drupal\language\Tests\EntityUrlLanguageTest.

language.module in core/modules/language/language.module

Add language handling functionality to Drupal.

LanguageNegotiationContentEntityTest.php in core/modules/language/src/Tests/LanguageNegotiationContentEntityTest.php

Contains \Drupal\language\Tests\LanguageNegotiationLanguageContentEntityTest.

LanguageNegotiationUrlTest.php in core/modules/language/tests/src/Unit/LanguageNegotiationUrlTest.php

Contains \Drupal\Tests\language\Unit\LanguageNegotiationUrlTest.

LanguageSwitchingTest.php in core/modules/language/src/Tests/LanguageSwitchingTest.php

Contains \Drupal\language\Tests\LanguageSwitchingTest.

LanguageUILanguageNegotiationTest.php in core/modules/language/src/Tests/LanguageUILanguageNegotiationTest.php

Contains \Drupal\language\Tests\LanguageUILanguageNegotiationTest.

LanguageUrlRewritingTest.php in core/modules/language/src/Tests/LanguageUrlRewritingTest.php

Contains \Drupal\language\Tests\LanguageUrlRewritingTest.

NegotiationUrlForm.php in core/modules/language/src/Form/NegotiationUrlForm.php

Contains \Drupal\language\Form\NegotiationUrlForm.

NodeFieldMultilingualTest.php in core/modules/node/src/Tests/NodeFieldMultilingualTest.php

Contains \Drupal\node\Tests\NodeFieldMultilingualTest.

PathProcessorTest.php in core/tests/Drupal/Tests/Core/PathProcessor/PathProcessorTest.php

Contains \Drupal\Tests\Core\PathProcessor\PathProcessorTest.