25 files declare their use of SystemConfigFormBase

AccountSettingsForm.php in drupal/core/modules/user/lib/Drupal/user/AccountSettingsForm.php
Contains \Drupal\user\AccountSettingsForm.
AdvancedSettingsForm.php in drupal/core/modules/views_ui/lib/Drupal/views_ui/Form/AdvancedSettingsForm.php
Contains \Drupal\views_ui\Form\AdvancedSettingsForm.
BasicSettingsForm.php in drupal/core/modules/views_ui/lib/Drupal/views_ui/Form/BasicSettingsForm.php
Contains \Drupal\views_ui\Form\BasicSettingsForm.
BookSettingsForm.php in drupal/core/modules/book/lib/Drupal/book/BookSettingsForm.php
Contains \Drupal\book\BookSettingsForm.
CronForm.php in drupal/core/modules/system/lib/Drupal/system/Form/CronForm.php
Contains \Drupal\system\Form\CronForm.
FileSystemForm.php in drupal/core/modules/system/lib/Drupal/system/Form/FileSystemForm.php
Contains \Drupal\system\Form\FileSystemForm.
ForumSettingsForm.php in drupal/core/modules/forum/lib/Drupal/forum/ForumSettingsForm.php
Contains \Drupal\forum\ForumSettingsForm.
ImageToolkitForm.php in drupal/core/modules/system/lib/Drupal/system/Form/ImageToolkitForm.php
Contains \Drupal\system\Form\ImageToolkitForm.
LocaleSettingsForm.php in drupal/core/modules/locale/lib/Drupal/locale/Form/LocaleSettingsForm.php
Contains \Drupal\user\LocaleSettingsForm.
LoggingForm.php in drupal/core/modules/system/lib/Drupal/system/Form/LoggingForm.php
Contains \Drupal\system\Form\LoggingForm.
MenuSettingsForm.php in drupal/core/modules/menu/lib/Drupal/menu/MenuSettingsForm.php
Contains \Drupal\menu\MenuSettingsForm.
NegotiationSelectedForm.php in drupal/core/modules/language/lib/Drupal/language/Form/NegotiationSelectedForm.php
Contains \Drupal\language\Form\NegotiationSelectedForm.
NegotiationSessionForm.php in drupal/core/modules/language/lib/Drupal/language/Form/NegotiationSessionForm.php
Contains \Drupal\language\Form\NegotiationSessionForm.
NegotiationUrlForm.php in drupal/core/modules/language/lib/Drupal/language/Form/NegotiationUrlForm.php
Contains \Drupal\language\Form\NegotiationUrlForm.
PerformanceForm.php in drupal/core/modules/system/lib/Drupal/system/Form/PerformanceForm.php
Contains \Drupal\system\Form\PerformanceForm.
RegionalForm.php in drupal/core/modules/system/lib/Drupal/system/Form/RegionalForm.php
Contains \Drupal\system\Form\RegionalForm.
RssFeedsForm.php in drupal/core/modules/system/lib/Drupal/system/Form/RssFeedsForm.php
Contains \Drupal\system\Form\RssFeedsForm.
SearchSettingsForm.php in drupal/core/modules/search/lib/Drupal/search/Form/SearchSettingsForm.php
Contains \Drupal\search\Form\SearchSettingsForm.
SettingsForm.php in drupal/core/modules/aggregator/lib/Drupal/aggregator/Form/SettingsForm.php
Contains \Drupal\aggregator\Form\SettingsForm.
SimpletestSettingsForm.php in drupal/core/modules/simpletest/lib/Drupal/simpletest/Form/SimpletestSettingsForm.php
Contains \Drupal\simpletest\Form\SimpletestSettingsForm.
SiteInformationForm.php in drupal/core/modules/system/lib/Drupal/system/Form/SiteInformationForm.php
Contains \Drupal\system\Form\SiteInformationForm.
SiteMaintenanceModeForm.php in drupal/core/modules/system/lib/Drupal/system/Form/SiteMaintenanceModeForm.php
Contains \Drupal\system\Form\SiteMaintenanceModeForm.
StatisticsSettingsForm.php in drupal/core/modules/statistics/lib/Drupal/statistics/StatisticsSettingsForm.php
Contains \Drupal\statistics\StatisticsSettingsForm.
SystemConfigFormTestForm.php in drupal/core/modules/system/tests/modules/form_test/lib/Drupal/form_test/SystemConfigFormTestForm.php
Contains \Drupal\form_test\SystemConfigFormTestForm.
UpdateSettingsForm.php in drupal/core/modules/update/lib/Drupal/update/UpdateSettingsForm.php
Contains \Drupal\update\UpdateSettingsForm.