diff --git a/core/lib/Drupal/Core/Plugin/Discovery/AnnotatedClassDiscovery.php b/core/lib/Drupal/Core/Plugin/Discovery/AnnotatedClassDiscovery.php
index 8a45afc..50c4635 100644
--- a/core/lib/Drupal/Core/Plugin/Discovery/AnnotatedClassDiscovery.php
+++ b/core/lib/Drupal/Core/Plugin/Discovery/AnnotatedClassDiscovery.php
@@ -8,6 +8,10 @@
 namespace Drupal\Core\Plugin\Discovery;
 
 use Drupal\Component\Plugin\Discovery\AnnotatedClassDiscovery as ComponentAnnotatedClassDiscovery;
+use Doctrine\Common\Annotations\AnnotationReader;
+use Doctrine\Common\Annotations\AnnotationRegistry;
+use Drupal\Component\Reflection\MockFileFinder;
+use Doctrine\Common\Reflection\StaticReflectionParser;
 
 /**
  * Defines a discovery mechanism to find annotated plugins in PSR-0 namespaces.
@@ -63,6 +67,52 @@ function __construct($subdir, \Traversable $root_namespaces, $annotation_namespa
   }
 
   /**
+   * Implements Drupal\Component\Plugin\Discovery\DiscoveryInterface::getDefinitions().
+   */
+  public function getDefinitions() {
+    $definitions = array();
+    $reader = new AnnotationReader();
+    // Prevent @endlink from being parsed as an annotation.
+    $reader->addGlobalIgnoredName('endlink');
+
+    // Register the namespaces of classes that can be used for annotations.
+    AnnotationRegistry::registerAutoloadNamespaces($this->getAnnotationNamespaces());
+
+    // Search for classes within all PSR-0 namespace locations.
+    foreach ($this->getPluginNamespaces() as $namespace => $dirs) {
+      // Extract the module name from this namespace.
+      $module = $this->getModuleFromNamespace($namespace);
+      foreach ($dirs as $dir) {
+        $dir .= DIRECTORY_SEPARATOR . str_replace('\\', DIRECTORY_SEPARATOR, $namespace);
+        if (file_exists($dir)) {
+          foreach (new \DirectoryIterator($dir) as $fileinfo) {
+            // @todo Once core requires 5.3.6, use $fileinfo->getExtension().
+            if (pathinfo($fileinfo->getFilename(), PATHINFO_EXTENSION) == 'php') {
+              $class = $namespace . '\\' . $fileinfo->getBasename('.php');
+
+              // The filename is already known, so there is no need to find the
+              // file. However, StaticReflectionParser needs a finder, so use a
+              // mock version.
+              $finder = MockFileFinder::create($fileinfo->getPathName());
+              $parser = new StaticReflectionParser($class, $finder);
+
+              if ($annotation = $reader->getClassAnnotation($parser->getReflectionClass(), $this->pluginDefinitionAnnotationName)) {
+                // AnnotationInterface::get() returns the array definition
+                // instead of requiring us to work with the annotation object.
+                $definition = $annotation->get();
+                $definition['class'] = $class;
+                $definition['module'] = $module;
+                $definitions[$definition['id']] = $definition;
+              }
+            }
+          }
+        }
+      }
+    }
+    return $definitions;
+  }
+
+  /**
    * {@inheritdoc}
    */
   protected function getPluginNamespaces() {
@@ -74,4 +124,23 @@ protected function getPluginNamespaces() {
     return $plugin_namespaces;
   }
 
+  /**
+   * Extracts a module name from a Drupal namespace.
+   *
+   * @param string $namespace
+   *   The namespace to extract the module name from.
+   *
+   * @return string|null
+   *   The matches module name, or NULL otherwise.
+   */
+  protected function getModuleFromNamespace($namespace) {
+    preg_match('|^Drupal\\\\(?<module>[\w]+)\\\\|', $namespace, $matches);
+
+    if (isset($matches['module'])) {
+      return $matches['module'];
+    }
+
+    return NULL;
+  }
+
 }