diff --git a/core/lib/Drupal/Component/Plugin/Discovery/ObjectDefinitionDiscoveryDecorator.php b/core/lib/Drupal/Component/Annotation/Plugin/Discovery/AnnotationBridgeDecorator.php
similarity index 77%
rename from core/lib/Drupal/Component/Plugin/Discovery/ObjectDefinitionDiscoveryDecorator.php
rename to core/lib/Drupal/Component/Annotation/Plugin/Discovery/AnnotationBridgeDecorator.php
index 985709c..53d70d1 100644
--- a/core/lib/Drupal/Component/Plugin/Discovery/ObjectDefinitionDiscoveryDecorator.php
+++ b/core/lib/Drupal/Component/Annotation/Plugin/Discovery/AnnotationBridgeDecorator.php
@@ -1,14 +1,14 @@
 <?php
 
-namespace Drupal\Component\Plugin\Discovery;
+namespace Drupal\Component\Annotation\Plugin\Discovery;
 
 use Drupal\Component\Plugin\Discovery\DiscoveryInterface;
 use Drupal\Component\Plugin\Discovery\DiscoveryTrait;
 
 /**
- * Ensures that all array-based definitions are converted to objects.
+ * Ensures that all definitions are run through the annotation process.
  */
-class ObjectDefinitionDiscoveryDecorator implements DiscoveryInterface {
+class AnnotationBridgeDecorator implements DiscoveryInterface {
 
   use DiscoveryTrait;
 
@@ -22,9 +22,6 @@ class ObjectDefinitionDiscoveryDecorator implements DiscoveryInterface {
   /**
    * The name of the annotation that contains the plugin definition.
    *
-   * The class corresponding to this name must implement
-   * \Drupal\Component\Annotation\AnnotationInterface.
-   *
    * @var string|null
    */
   protected $pluginDefinitionAnnotationName;
@@ -35,7 +32,9 @@ class ObjectDefinitionDiscoveryDecorator implements DiscoveryInterface {
    * @param \Drupal\Component\Plugin\Discovery\DiscoveryInterface $decorated
    *   The discovery object that is being decorated.
    * @param string $plugin_definition_annotation_name
-   *   The name of the annotation that contains the plugin definition.
+   *   The name of the annotation that contains the plugin definition. The class
+   *   corresponding to this name must implement
+   *   \Drupal\Component\Annotation\AnnotationInterface.
    */
   public function __construct(DiscoveryInterface $decorated, $plugin_definition_annotation_name) {
     $this->decorated = $decorated;
@@ -48,6 +47,9 @@ public function __construct(DiscoveryInterface $decorated, $plugin_definition_an
   public function getDefinitions() {
     $definitions = $this->decorated->getDefinitions();
     foreach ($definitions as $id => $definition) {
+      // Annotation constructors expect an array of values. If the definition is
+      // not an array, it usually means it has been processed already and can be
+      // ignored.
       if (is_array($definition)) {
         $definitions[$id] = (new $this->pluginDefinitionAnnotationName($definition))->get();
       }
diff --git a/core/lib/Drupal/Core/Layout/LayoutPluginManager.php b/core/lib/Drupal/Core/Layout/LayoutPluginManager.php
index 23fa9f1..e1d0a1e 100644
--- a/core/lib/Drupal/Core/Layout/LayoutPluginManager.php
+++ b/core/lib/Drupal/Core/Layout/LayoutPluginManager.php
@@ -2,7 +2,7 @@
 
 namespace Drupal\Core\Layout;
 
-use Drupal\Component\Plugin\Discovery\ObjectDefinitionDiscoveryDecorator;
+use Drupal\Component\Annotation\Plugin\Discovery\AnnotationBridgeDecorator;
 use Drupal\Component\Plugin\Exception\InvalidPluginDefinitionException;
 use Drupal\Core\Cache\CacheBackendInterface;
 use Drupal\Core\Extension\ModuleHandlerInterface;
@@ -64,7 +64,7 @@ protected function getDiscovery() {
     if (!$this->discovery) {
       $discovery = new AnnotatedClassDiscovery($this->subdir, $this->namespaces, $this->pluginDefinitionAnnotationName, $this->additionalAnnotationNamespaces);
       $discovery = new YamlDiscoveryDecorator($discovery, 'layouts', $this->moduleHandler->getModuleDirectories() + $this->themeHandler->getThemeDirectories());
-      $discovery = new ObjectDefinitionDiscoveryDecorator($discovery, $this->pluginDefinitionAnnotationName);
+      $discovery = new AnnotationBridgeDecorator($discovery, $this->pluginDefinitionAnnotationName);
       $discovery = new ObjectDefinitionContainerDerivativeDiscoveryDecorator($discovery);
       $this->discovery = $discovery;
     }
diff --git a/core/tests/Drupal/Tests/Component/Annotation/Plugin/Discovery/AnnotationBridgeDecoratorTest.php b/core/tests/Drupal/Tests/Component/Annotation/Plugin/Discovery/AnnotationBridgeDecoratorTest.php
new file mode 100644
index 0000000..c1e231e
--- /dev/null
+++ b/core/tests/Drupal/Tests/Component/Annotation/Plugin/Discovery/AnnotationBridgeDecoratorTest.php
@@ -0,0 +1,61 @@
+<?php
+
+namespace Drupal\Tests\Component\Annotation\Plugin\Discovery;
+
+use Drupal\Component\Annotation\Plugin;
+use Drupal\Component\Annotation\Plugin\Discovery\AnnotationBridgeDecorator;
+use Drupal\Component\Plugin\Definition\PluginDefinition;
+use Drupal\Component\Plugin\Discovery\DiscoveryInterface;
+use Drupal\Tests\UnitTestCase;
+
+/**
+ * @coversDefaultClass \Drupal\Component\Annotation\Plugin\Discovery\AnnotationBridgeDecorator
+ * @group Plugin
+ */
+class AnnotationBridgeDecoratorTest extends UnitTestCase {
+
+  /**
+   * @covers ::getDefinitions
+   */
+  public function testGetDefinitions() {
+    $definitions = [];
+    $definitions['object'] = new ObjectDefinition(['id' => 'foo']);
+    $definitions['array'] = ['id' => 'bar'];
+    $discovery = $this->prophesize(DiscoveryInterface::class);
+    $discovery->getDefinitions()->willReturn($definitions);
+
+    $decorator = new AnnotationBridgeDecorator($discovery->reveal(), TestAnnotation::class);
+
+    $expected = [
+      'object' => new ObjectDefinition(['id' => 'foo']),
+      'array' => new ObjectDefinition(['id' => 'bar']),
+    ];
+    $this->assertEquals($expected, $decorator->getDefinitions());
+  }
+
+}
+
+class TestAnnotation extends Plugin {
+
+  /**
+   * {@inheritdoc}
+   */
+  public function get() {
+    return new ObjectDefinition($this->definition);
+  }
+
+}
+class ObjectDefinition extends PluginDefinition {
+
+  /**
+   * ObjectDefinition constructor.
+   *
+   * @param array $definition
+   */
+  public function __construct(array $definition) {
+    foreach ($definition as $property => $value) {
+      $this->{$property} = $value;
+    }
+  }
+
+}