6 files declare their use of ShortcutSet in Zircon Profile 8

MigrateShortcutSetTest.php in core/modules/shortcut/src/Tests/Migrate/d7/MigrateShortcutSetTest.php

Contains \Drupal\shortcut\Tests\Migrate\d7\MigrateShortcutSetTest.

shortcut.module in core/modules/shortcut/shortcut.module

Allows users to manage customizable lists of shortcut links.

ShortcutLinksTest.php in core/modules/shortcut/src/Tests/ShortcutLinksTest.php

Contains \Drupal\shortcut\Tests\ShortcutLinksTest.

ShortcutSetsTest.php in core/modules/shortcut/src/Tests/ShortcutSetsTest.php

Contains \Drupal\shortcut\Tests\ShortcutSetsTest.

ShortcutTestBase.php in core/modules/shortcut/src/Tests/ShortcutTestBase.php

Contains \Drupal\shortcut\Tests\ShortcutTestBase.

SwitchShortcutSet.php in core/modules/shortcut/src/Form/SwitchShortcutSet.php

Contains \Drupal\shortcut\Form\SwitchShortcutSet.