15 files declare their use of PagerSelectExtender

CommentStorage.php in core/modules/comment/src/CommentStorage.php
DatabaseTestController.php in core/modules/system/tests/modules/database_test/src/Controller/DatabaseTestController.php
DatabaseTestForm.php in core/modules/system/tests/modules/database_test/src/Form/DatabaseTestForm.php
DbLogController.php in core/modules/dblog/src/Controller/DbLogController.php
ForumManager.php in core/modules/forum/src/ForumManager.php
HelpSearch.php in core/modules/help_topics/src/Plugin/Search/HelpSearch.php
NodeSearch.php in core/modules/node/src/Plugin/Search/NodeSearch.php
PagerManager.php in core/lib/Drupal/Core/Pager/PagerManager.php
PagerSelectExtender.php in core/tests/fixtures/database_drivers/module/corefake/src/Driver/Database/corefakeWithAllCustomClasses/PagerSelectExtender.php
PagerTestController.php in core/modules/system/tests/modules/pager_test/src/Controller/PagerTestController.php
SelectComplexTest.php in core/tests/Drupal/KernelTests/Core/Database/SelectComplexTest.php
SelectPagerDefaultTest.php in core/modules/system/tests/src/Functional/Database/SelectPagerDefaultTest.php
StringDatabaseStorage.php in core/modules/locale/src/StringDatabaseStorage.php
TrackerController.php in core/modules/tracker/src/Controller/TrackerController.php
UserSearch.php in core/modules/user/src/Plugin/Search/UserSearch.php

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