21 files declare their use of PublicStream in Drupal 8

CachedStorageTest.php in core/tests/Drupal/KernelTests/Core/Config/Storage/CachedStorageTest.php

DummyRemoteStreamWrapper.php in core/modules/file/tests/file_test/src/StreamWrapper/DummyRemoteStreamWrapper.php

FileStorageTest.php in core/tests/Drupal/KernelTests/Core/Config/Storage/FileStorageTest.php

FileSystem.php in core/lib/Drupal/Core/File/FileSystem.php

FileSystemForm.php in core/modules/system/src/Form/FileSystemForm.php

FileTransferTest.php in core/modules/system/tests/src/Functional/FileTransfer/FileTransferTest.php

FilterHtmlImageSecureTest.php in core/modules/filter/tests/src/Functional/FilterHtmlImageSecureTest.php

ImageStyleCustomStreamWrappersTest.php in core/modules/image/tests/src/Kernel/ImageStyleCustomStreamWrappersTest.php

LocaleTranslationDownloadTest.php in core/modules/locale/tests/src/Functional/LocaleTranslationDownloadTest.php

LocaleUpdateBase.php in core/modules/locale/tests/src/Functional/LocaleUpdateBase.php

locale_test.module in core/modules/locale/tests/modules/locale_test/locale_test.module

Simulate a custom module with a local po file.

PhpStorageFactory.php in core/lib/Drupal/Core/PhpStorage/PhpStorageFactory.php

PhpStorageFactoryTest.php in core/modules/system/tests/src/Kernel/PhpStorage/PhpStorageFactoryTest.php

simpletest.module in core/modules/simpletest/simpletest.module

Provides testing functionality.

StreamWrapperTest.php in core/tests/Drupal/KernelTests/Core/File/StreamWrapperTest.php

system.install in core/modules/system/system.install

Install, update and uninstall functions for the system module.

TestBase.php in core/modules/simpletest/src/TestBase.php

TestDeprecatedTestHooks.php in core/modules/simpletest/tests/src/Kernel/TestDeprecatedTestHooks.php

TestFileCreationTrait.php in core/tests/Drupal/Tests/TestFileCreationTrait.php

ThemeSettingsForm.php in core/modules/system/src/Form/ThemeSettingsForm.php

ThemeTest.php in core/modules/system/tests/src/Functional/System/ThemeTest.php