6 files declare their use of ContactForm in Zircon Profile 8

ContactSitewideTest.php in core/modules/contact/src/Tests/ContactSitewideTest.php

Contains \Drupal\contact\Tests\ContactSitewideTest.

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

Contains \Drupal\system\Tests\Entity\ContentEntityNullStorageTest.

MigrateContactCategoryTest.php in core/modules/contact/src/Tests/Migrate/MigrateContactCategoryTest.php

Contains \Drupal\contact\Tests\Migrate\MigrateContactCategoryTest.

MigrateContactCategoryTest.php in core/modules/contact/src/Tests/Migrate/d6/MigrateContactCategoryTest.php

Contains \Drupal\contact\Tests\Migrate\d6\MigrateContactCategoryTest.

standard.profile in core/profiles/standard/standard.profile

Enables modules and site configuration for a standard site installation.

StandardTest.php in core/profiles/standard/src/Tests/StandardTest.php

Contains \Drupal\standard\Tests\StandardTest.