9 files declare their use of ServiceModifierInterface in Zircon Profile 8

AcceptHeaderRoutingTestServiceProvider.php in core/modules/system/tests/modules/accept_header_routing_test/src/AcceptHeaderRoutingTestServiceProvider.php

Contains \Drupal\accept_header_routing_test\AcceptHeaderRoutingTestServiceProvider.

DrupalKernel.php in core/lib/Drupal/Core/DrupalKernel.php

Contains \Drupal\Core\DrupalKernel.

ErrorServiceTestServiceProvider.php in core/modules/system/tests/modules/error_service_test/src/ErrorServiceTestServiceProvider.php

Contains \Drupal\error_service_test\ErrorServiceTestServiceProvider.

HalServiceProvider.php in core/modules/hal/src/HalServiceProvider.php

Contains \Drupal\hal\HalServiceProvider.

InstallerServiceProvider.php in core/lib/Drupal/Core/Installer/InstallerServiceProvider.php

Contains \Drupal\Core\Installer\InstallerServiceProvider.

ModifyServiceDefinitionsPass.php in core/lib/Drupal/Core/DependencyInjection/Compiler/ModifyServiceDefinitionsPass.php

Contains \Drupal\Core\DependencyInjection\Compiler\ModifyServiceDefinitionsPass.

ServiceProviderTestServiceProvider.php in core/modules/system/tests/modules/service_provider_test/src/ServiceProviderTestServiceProvider.php

Contains \Drupal\service_provider_test\ServiceProviderTestServiceProvider.

UpdateServiceProvider.php in core/lib/Drupal/Core/Update/UpdateServiceProvider.php

Contains \Drupal\Core\Update\UpdateServiceProvider.

UserServiceProvider.php in core/modules/user/src/UserServiceProvider.php

Contains \Drupal\user\UserServiceProvider.