3 files declare their use of ViewsForm

claro.theme in core/themes/claro/claro.theme: Functions to support theming in the Claro theme.
DisplayPluginBase.php in core/modules/views/src/Plugin/views/display/DisplayPluginBase.php
umami.theme in core/profiles/demo_umami/themes/umami/umami.theme: Functions to support theming in the Umami theme.

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