7 files declare their use of UseCacheBackendTrait

DefaultPluginManager.php in core/lib/Drupal/Core/Plugin/DefaultPluginManager.php
EntityDisplayRepository.php in core/lib/Drupal/Core/Entity/EntityDisplayRepository.php
EntityFieldManager.php in core/lib/Drupal/Core/Entity/EntityFieldManager.php
EntityTypeBundleInfo.php in core/lib/Drupal/Core/Entity/EntityTypeBundleInfo.php
ProviderRepository.php in core/modules/media/src/OEmbed/ProviderRepository.php
ResourceFetcher.php in core/modules/media/src/OEmbed/ResourceFetcher.php
UrlResolver.php in core/modules/media/src/OEmbed/UrlResolver.php

Buggy or inaccurate documentation? Please file an issue. Need support? Need help programming? Connect with the Drupal community.