11 files declare their use of Bytes in Drupal 8

BytesTest.php in core/tests/Drupal/Tests/Component/Utility/BytesTest.php

color.module in core/modules/color/color.module

Allows users to change the color scheme of themes.

common.inc in core/includes/common.inc

Common functions that many Drupal modules will need to reference.

EditorImageDialog.php in core/modules/editor/src/Form/EditorImageDialog.php

FileItem.php in core/modules/file/src/Plugin/Field/FieldType/FileItem.php

FileUploadResource.php in core/modules/file/src/Plugin/rest/resource/FileUploadResource.php

MaximumFileSizeExceededUploadTest.php in core/modules/file/tests/src/FunctionalJavascript/MaximumFileSizeExceededUploadTest.php

MigrateExecutable.php in core/modules/migrate/src/MigrateExecutable.php

SizeTest.php in core/tests/Drupal/KernelTests/Core/Common/SizeTest.php

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

Install, update and uninstall functions for the system module.

TemporaryJsonapiFileFieldUploader.php in core/modules/jsonapi/src/Controller/TemporaryJsonapiFileFieldUploader.php