20 files declare their use of Environment in Drupal 8

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.

Cron.php in core/lib/Drupal/Core/Cron.php

editor.admin.inc in core/modules/editor/editor.admin.inc

Administration functions for editor.module.

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

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

file.inc in core/includes/file.inc

API for handling file uploads and server file management.

file.module in core/modules/file/file.module

Defines a "managed_file" Form API field and a "file" field for Field module.

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

FileModuleTest.php in core/modules/file/tests/src/Kernel/FileModuleTest.php

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

FormBuilder.php in core/lib/Drupal/Core/Form/FormBuilder.php

FunctionalTestSetupTrait.php in core/lib/Drupal/Core/Test/FunctionalTestSetupTrait.php

ImportForm.php in core/modules/locale/src/Form/ImportForm.php

LargeQueryTest.php in core/tests/Drupal/KernelTests/Core/Database/LargeQueryTest.php

node.module in core/modules/node/node.module

The core module that allows content to be submitted to the site.

simpletest.install in core/modules/simpletest/simpletest.install

Install, update and uninstall functions for the simpletest module.

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

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