12 files declare their use of Bundle

BundleTest.php in drupal/core/vendor/symfony/http-kernel/Symfony/Component/HttpKernel/Tests/Bundle/BundleTest.php
CoreBundle.php in drupal/core/lib/Drupal/Core/CoreBundle.php
Definition of Drupal\Core\CoreBundle.
ExtensionAbsentBundle.php in drupal/core/vendor/symfony/http-kernel/Symfony/Component/HttpKernel/Tests/Fixtures/ExtensionAbsentBundle/ExtensionAbsentBundle.php
ExtensionLoadedBundle.php in drupal/core/vendor/symfony/http-kernel/Symfony/Component/HttpKernel/Tests/Fixtures/ExtensionLoadedBundle/ExtensionLoadedBundle.php
ExtensionPresentBundle.php in drupal/core/vendor/symfony/http-kernel/Symfony/Component/HttpKernel/Tests/Fixtures/ExtensionPresentBundle/ExtensionPresentBundle.php
FooBarBundle.php in drupal/core/vendor/symfony/http-kernel/Symfony/Component/HttpKernel/Tests/Fixtures/FooBarBundle.php
KernelTest.php in drupal/core/vendor/symfony/http-kernel/Symfony/Component/HttpKernel/Tests/KernelTest.php
LanguageTestBundle.php in drupal/core/modules/language/tests/language_test/lib/Drupal/language_test/LanguageTestBundle.php
Contains \Drupal\language_test\LanguageTestBundle.
RouterTestBundle.php in drupal/core/modules/system/tests/modules/router_test/lib/Drupal/router_test/RouterTestBundle.php
Definition of \Drupal\router_test\RouterTestBundle.
SerializationBundle.php in drupal/core/modules/serialization/lib/Drupal/serialization/SerializationBundle.php
Contains \Drupal\serialization\SerializationBundle.
TestBundle.php in drupal/core/modules/simpletest/lib/Drupal/simpletest/TestBundle.php
UpdateBundle.php in drupal/core/lib/Drupal/Core/DependencyInjection/UpdateBundle.php
Contains \Drupal\Core\DependencyInjection\UpdateBundle.