Issue #2026347 by Berdir: Adding methods to UserInterface/AccountInterface.

core/includes/theme.inc

core/lib/Drupal/Core/Session/AccountInterface.php

core/lib/Drupal/Core/Session/UserSession.php

...es/action/lib/Drupal/action/Plugin/Action/EmailAction.php

...ules/contact/lib/Drupal/contact/MessageFormController.php

core/modules/dblog/dblog.admin.inc

...les/dblog/lib/Drupal/dblog/Controller/DbLogController.php

core/modules/forum/forum.module

core/modules/language/language.module

core/modules/language/language.negotiation.inc

...dules/locale/lib/Drupal/locale/LocaleConfigSubscriber.php

core/modules/node/node.admin.inc

core/modules/node/node.module

core/modules/node/node.pages.inc

core/modules/rest/lib/Drupal/rest/Access/CSRFAccessCheck.php

...m/lib/Drupal/system/Tests/Upgrade/UpgradePathTestBase.php

core/modules/tracker/tracker.pages.inc

core/modules/update/update.fetch.inc

core/modules/user/lib/Drupal/user/AccountFormController.php

...Drupal/user/EventSubscriber/MaintenanceModeSubscriber.php