13 files declare their use of Event

ConfigEvent.php in drupal/core/lib/Drupal/Core/Config/ConfigEvent.php
ConfigImporterEvent.php in drupal/core/lib/Drupal/Core/Config/ConfigImporterEvent.php
Contains \Drupal\Core\Config\ConfigImporterEvent.
ContainerAwareEventDispatcherTest.php in drupal/core/vendor/symfony/event-dispatcher/Symfony/Component/EventDispatcher/Tests/ContainerAwareEventDispatcherTest.php
Event.php in drupal/core/vendor/guzzle/common/Guzzle/Common/Event.php
EventDispatcherTest.php in drupal/core/vendor/symfony/event-dispatcher/Symfony/Component/EventDispatcher/Tests/EventDispatcherTest.php
EventTest.php in drupal/core/vendor/symfony/event-dispatcher/Symfony/Component/EventDispatcher/Tests/EventTest.php
ImmutableEventDispatcherTest.php in drupal/core/vendor/symfony/event-dispatcher/Symfony/Component/EventDispatcher/Tests/ImmutableEventDispatcherTest.php
KernelEvent.php in drupal/core/vendor/symfony/http-kernel/Symfony/Component/HttpKernel/Event/KernelEvent.php
MapTypesFromInputEvent.php in drupal/core/modules/rdf/lib/Drupal/rdf/MapTypesFromInputEvent.php
Contains MapInputTypesEvent.
PostResponseEvent.php in drupal/core/vendor/symfony/http-kernel/Symfony/Component/HttpKernel/Event/PostResponseEvent.php
RouteBuildEvent.php in drupal/core/lib/Drupal/Core/Routing/RouteBuildEvent.php
Definition of Drupal\Core\Routing\RouteBuildEvent.
TraceableEventDispatcher.php in drupal/core/vendor/symfony/http-kernel/Symfony/Component/HttpKernel/Debug/TraceableEventDispatcher.php
TraceableEventDispatcherTest.php in drupal/core/vendor/symfony/http-kernel/Symfony/Component/HttpKernel/Tests/Debug/TraceableEventDispatcherTest.php