31 files declare their use of MainContentViewSubscriber in Drupal 8

AjaxFormCacheTest.php in core/tests/Drupal/FunctionalJavascriptTests/Ajax/AjaxFormCacheTest.php

AjaxHelperTrait.php in core/lib/Drupal/Core/Ajax/AjaxHelperTrait.php

AreaDisplayLinkTest.php in core/modules/views/tests/src/Kernel/Handler/AreaDisplayLinkTest.php

BlockLibraryController.php in core/modules/block/src/Controller/BlockLibraryController.php

ContentModerationConfigureEntityTypesForm.php in core/modules/content_moderation/src/Form/ContentModerationConfigureEntityTypesForm.php

DisplayLink.php in core/modules/views/src/Plugin/views/area/DisplayLink.php

DynamicPageCacheIntegrationTest.php in core/modules/dynamic_page_cache/tests/src/Functional/DynamicPageCacheIntegrationTest.php

EntityCacheTagsTestBase.php in core/modules/system/src/Tests/Entity/EntityCacheTagsTestBase.php

EntityCacheTagsTestBase.php in core/modules/system/tests/src/Functional/Entity/EntityCacheTagsTestBase.php

FormAjaxSubscriber.php in core/lib/Drupal/Core/Form/EventSubscriber/FormAjaxSubscriber.php

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

FrameworkTest.php in core/modules/system/tests/src/Functional/Ajax/FrameworkTest.php

MenuUiTest.php in core/modules/menu_ui/tests/src/Functional/MenuUiTest.php

NodeBlockFunctionalTest.php in core/modules/node/tests/src/Functional/NodeBlockFunctionalTest.php

OffCanvasDialogTest.php in core/modules/system/tests/src/Functional/Ajax/OffCanvasDialogTest.php

PageCacheTagsIntegrationTest.php in core/modules/page_cache/tests/src/Functional/PageCacheTagsIntegrationTest.php

QuickEditCustomPipelineTest.php in core/modules/quickedit/tests/src/Functional/QuickEditCustomPipelineTest.php

QuickEditEndPointAccessTest.php in core/modules/quickedit/tests/src/Functional/QuickEditEndPointAccessTest.php

QuickEditIntegrationLoadingTest.php in core/modules/editor/tests/src/Functional/QuickEditIntegrationLoadingTest.php

RenderWebTest.php in core/modules/system/tests/src/Functional/Common/RenderWebTest.php

RouterTest.php in core/modules/system/tests/src/Functional/Routing/RouterTest.php

StackSessionHandlerIntegrationTest.php in core/modules/system/tests/src/Functional/Session/StackSessionHandlerIntegrationTest.php

StorageTest.php in core/modules/system/tests/src/Functional/Form/StorageTest.php

StyleSerializerTest.php in core/modules/rest/tests/src/Functional/Views/StyleSerializerTest.php

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

ToolbarAdminMenuTest.php in core/modules/toolbar/tests/src/Functional/ToolbarAdminMenuTest.php

ToolbarCacheContextsTest.php in core/modules/toolbar/tests/src/Functional/ToolbarCacheContextsTest.php

TrackerTest.php in core/modules/tracker/tests/src/Functional/TrackerTest.php

ViewAjaxController.php in core/modules/views/src/Controller/ViewAjaxController.php

ViewAjaxTest.php in core/modules/views/tests/src/Functional/ViewAjaxTest.php

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