12 files declare their use of Settings

bootstrap.inc in drupal/core/includes/bootstrap.inc
Functions that need to be loaded on every Drupal request.
BootstrapConfigStorageFactory.php in drupal/core/lib/Drupal/Core/Config/BootstrapConfigStorageFactory.php
Contains Drupal\Core\Config\BootstrapConfigStorageFactory.
CacheFactory.php in drupal/core/lib/Drupal/Core/Cache/CacheFactory.php
Contains \Drupal\Core\Cache\CacheFactory.
PathProcessorLanguage.php in drupal/core/modules/language/lib/Drupal/language/HttpKernel/PathProcessorLanguage.php
Contains Drupal\language\HttpKernel\PathProcessorLanguage.
PathProcessorTest.php in drupal/core/tests/Drupal/Tests/Core/PathProcessor/PathProcessorTest.php
Contains Drupal\Tests\Core\PathProcessor\PathProcessorTest.
QueueFactory.php in drupal/core/lib/Drupal/Core/Queue/QueueFactory.php
Contains \Drupal\Core\Queue\QueueFactory.
ReverseProxySubscriber.php in drupal/core/lib/Drupal/Core/EventSubscriber/ReverseProxySubscriber.php
Contains \Drupal\Core\EventSubscriber\ReverseProxySubscriber.
ReverseProxySubscriberUnitTest.php in drupal/core/tests/Drupal/Tests/Core/EventSubscriber/ReverseProxySubscriberUnitTest.php
Contains \Drupal\Core\EventSubscriber\ReverseProxySubscriberUnitTest.
TestBase.php in drupal/core/modules/simpletest/lib/Drupal/simpletest/TestBase.php
Definition of Drupal\simpletest\TestBase.
update.inc in drupal/core/includes/update.inc
Drupal database update API.
UrlGenerator.php in drupal/core/lib/Drupal/Core/Routing/UrlGenerator.php
Contains Drupal\Core\Routing\UrlGenerator.
UrlGeneratorTest.php in drupal/core/tests/Drupal/Tests/Core/Routing/UrlGeneratorTest.php
Contains Drupal\Tests\Core\Routing\UrlGeneratorTest.