7 files declare their use of AttachedAssets in Zircon Profile 8

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

Contains \Drupal\Core\Ajax\AjaxResponseAttachmentsProcessor.

AssetResolverTest.php in core/tests/Drupal/Tests/Core/Asset/AssetResolverTest.php

Contains \Drupal\Tests\Core\Asset\AssetResolverTest.

AttachedAssetsTest.php in core/modules/system/src/Tests/Common/AttachedAssetsTest.php

Contains \Drupal\system\Tests\Common\AttachedAssetsTest.

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

Contains \Drupal\Core\Ajax\CommandWithAttachedAssetsTrait.

FrameworkTest.php in core/modules/system/src/Tests/Ajax/FrameworkTest.php

Contains \Drupal\system\Tests\Ajax\FrameworkTest.

HtmlResponseAttachmentsProcessor.php in core/lib/Drupal/Core/Render/HtmlResponseAttachmentsProcessor.php

Contains \Drupal\Core\Render\HtmlResponseAttachmentsProcessor.

LocaleLibraryAlterTest.php in core/modules/locale/src/Tests/LocaleLibraryAlterTest.php

Contains \Drupal\locale\Tests\LocaleLibraryAlterTest.