Update to drupal 8.0.0-rc1. For more information, see https://www.drupal.org/node/2582663

core/lib/Drupal/Component/Plugin/Definition/PluginDefinitionInterface.php

@@ -0,0 +1,40 @@
+<?php
+
+/**
+ * @file
+ * Contains \Drupal\Component\Plugin\PluginDefinitionInterface.
+ */
+
+namespace Drupal\Component\Plugin\Definition;
+
+/**
+ * Defines a plugin definition.
+ *
+ * Object-based plugin definitions MUST implement this interface.
+ *
+ * @ingroup Plugin
+ */
+interface PluginDefinitionInterface {
+
+  /**
+   * Sets the class.
+   *
+   * @param string $class
+   *   A fully qualified class name.
+   *
+   * @return static
+   *
+   * @throws \InvalidArgumentException
+   *   If the class is invalid.
+   */
+  public function setClass($class);
+
+  /**
+   * Gets the class.
+   *
+   * @return string
+   *   A fully qualified class name.
+   */
+  public function getClass();
+
+}