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

core/modules/field/src/Tests/FieldDefaultValueCallbackProvider.php

@@ -0,0 +1,22 @@
+<?php
+
+/**
+ * @file
+ * Contains \Drupal\field\Tests\FieldDefaultValueCallbackProvider.
+ */
+
+namespace Drupal\field\Tests;
+
+/**
+ * Helper class for \Drupal\field\Tests\FieldDefaultValueCallbackTest.
+ */
+class FieldDefaultValueCallbackProvider {
+
+  /**
+   * Helper callback calculating a default value.
+   */
+  public static function calculateDefaultValue() {
+    return [['value' => 'Calculated default value']];
+  }
+
+}