diff --git a/core/lib/Drupal/Core/Entity/Plugin/DataType/EntityReferenceItem.php b/core/lib/Drupal/Core/Entity/Plugin/DataType/EntityReferenceItem.php
index 69b2400..6c70241 100644
--- a/core/lib/Drupal/Core/Entity/Plugin/DataType/EntityReferenceItem.php
+++ b/core/lib/Drupal/Core/Entity/Plugin/DataType/EntityReferenceItem.php
@@ -9,8 +9,8 @@
 
 use Drupal\Core\TypedData\Annotation\DataType;
 use Drupal\Core\Annotation\Translation;
-use Drupal\Core\Entity\Field\FieldItemBase;
-use Drupal\Core\TypedData\TypedDataInterface;
+use Drupal\field\Plugin\Type\FieldType\ConfigFieldItemBase;
+use Drupal\field\FieldInterface;
 
 /**
  * Defines the 'entity_reference_item' entity field item.
@@ -29,7 +29,7 @@
  *   constraints = {"ValidReference" = TRUE}
  * )
  */
-class EntityReferenceItem extends FieldItemBase {
+class EntityReferenceItem extends ConfigFieldItemBase {
 
   /**
    * Definitions of the contained properties.
@@ -41,7 +41,7 @@ class EntityReferenceItem extends FieldItemBase {
   static $propertyDefinitions;
 
   /**
-   * Implements \Drupal\Core\TypedData\ComplexDataInterface::getPropertyDefinitions().
+   * {@inheritdoc}
    */
   public function getPropertyDefinitions() {
     // Definitions vary by entity type and bundle, so key them accordingly.
@@ -76,7 +76,7 @@ public function getPropertyDefinitions() {
   }
 
   /**
-   * Overrides \Drupal\Core\Entity\Field\FieldItemBase::__get().
+   * {@inheritdoc}
    */
   public function __get($name) {
     $name = ($name == 'value') ? 'target_id' : $name;
@@ -84,7 +84,7 @@ public function __get($name) {
   }
 
   /**
-   * Overrides \Drupal\Core\Entity\Field\FieldItemBase::get().
+   * {@inheritdoc}
    */
   public function get($property_name) {
     $property_name = ($property_name == 'value') ? 'target_id' : $property_name;
@@ -92,7 +92,7 @@ public function get($property_name) {
   }
 
   /**
-   * Implements \Drupal\Core\Entity\Field\FieldItemInterface::__isset().
+   * {@inheritdoc}
    */
   public function __isset($property_name) {
     $property_name = ($property_name == 'value') ? 'target_id' : $property_name;
@@ -100,7 +100,7 @@ public function __isset($property_name) {
   }
 
   /**
-   * Overrides \Drupal\Core\Entity\Field\FieldItemBase::get().
+   * {@inheritdoc}
    */
   public function setValue($values, $notify = TRUE) {
     if (isset($values) && !is_array($values)) {
@@ -134,4 +134,40 @@ public function onChange($property_name) {
     }
     parent::onChange($property_name);
   }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function isEmpty() {
+    // Avoid loading the entity by first checking the 'target_id'.
+    $target_id = $this->get('target_id')->getValue();
+    if (!empty($target_id) && is_numeric($target_id)) {
+      return FALSE;
+    }
+    // Allow auto-create entities.
+    if (empty($target_id) && ($entity = $this->get('entity')->getValue()) && $entity->isNew()) {
+      return FALSE;
+    }
+    return TRUE;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public function preSave() {
+    $entity = $this->get('entity')->getValue();
+    $target_id = $this->get('target_id')->getValue();
+
+    if (empty($target_id) && !empty($entity) && $entity->isNew()) {
+      $entity->save();
+      $this->set('target_id', $entity->id());
+    }
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  public static function schema(FieldInterface $field) {
+    return array();
+  }
 }
diff --git a/core/modules/entity_reference/lib/Drupal/entity_reference/Plugin/field/field_type/ConfigurableEntityReferenceItem.php b/core/modules/entity_reference/lib/Drupal/entity_reference/Plugin/field/field_type/ConfigurableEntityReferenceItem.php
index ee5e79a..edf1530 100644
--- a/core/modules/entity_reference/lib/Drupal/entity_reference/Plugin/field/field_type/ConfigurableEntityReferenceItem.php
+++ b/core/modules/entity_reference/lib/Drupal/entity_reference/Plugin/field/field_type/ConfigurableEntityReferenceItem.php
@@ -9,11 +9,7 @@
 
 use Drupal\Core\Annotation\Translation;
 use Drupal\Core\Entity\Annotation\FieldType;
-use Drupal\Core\Entity\Field\Type\EntityReferenceItem;
-use Drupal\field\Plugin\Type\FieldType\ConfigEntityReferenceItemBase;
-use Drupal\field\Plugin\Type\FieldType\ConfigFieldItemBase;
-use Drupal\field\Plugin\Type\FieldType\ConfigFieldItemInterface;
-use Drupal\field\FieldInterface;
+use Drupal\Core\Entity\Plugin\DataType\EntityReferenceItem;
 
 /**
  * Plugin implementation of the 'entity_reference' field type.
@@ -40,60 +36,41 @@
  * Required settings (below the definition's 'settings' key) are:
  *  - target_type: The entity type to reference.
  */
-class ConfigurableEntityReferenceItem extends ConfigEntityReferenceItemBase implements ConfigFieldItemInterface {
+class ConfigurableEntityReferenceItem extends EntityReferenceItem {
 
   /**
    * {@inheritdoc}
    */
-  public static function schema(FieldInterface $field) {
-    $schema = array(
-      'columns' => array(
-        'target_id' => array(
-          'description' => 'The ID of the target entity.',
-          'type' => 'int',
-          'unsigned' => TRUE,
-          'not null' => TRUE,
+  public function getPropertyDefinitions() {
+    // Definitions vary by entity type and bundle, so key them accordingly.
+    $key = $this->definition['settings']['target_type'] . ':';
+    $key .= isset($this->definition['settings']['target_bundle']) ? $this->definition['settings']['target_bundle'] : '';
+
+    if (!isset(static::$propertyDefinitions[$key])) {
+      // Call the parent to define the target_id and entity properties.
+      parent::getPropertyDefinitions();
+
+      static::$propertyDefinitions[$key]['revision_id'] = array(
+
+        // @todo: Lookup the entity type's ID data type and use it here.
+        'type' => 'integer',
+        'label' => t('Revision ID'),
+        'constraints' => array(
+          'Range' => array('min' => 0),
         ),
-        'revision_id' => array(
-          'description' => 'The revision ID of the target entity.',
-          'type' => 'int',
-          'unsigned' => TRUE,
-          'not null' => FALSE,
-        ),
-      ),
-      'indexes' => array(
-        'target_id' => array('target_id'),
-      ),
-    );
-
-    // Create a foreign key to the target entity type base type.
-    $entity_manager = \Drupal::service('entity.manager');
-    if (is_subclass_of($entity_manager->getControllerClass($field['settings']['target_type'], 'storage'), 'Drupal\Core\Entity\DatabaseStorageController')) {
-      $entity_info = $entity_manager->getDefinition($field['settings']['target_type']);
-
-      $base_table = $entity_info['base_table'];
-      $id_column = $entity_info['entity_keys']['id'];
-
-      $schema['foreign keys'][$base_table] = array(
-        'table' => $base_table,
-        'columns' => array('target_id' => $id_column),
+      );
+      static::$propertyDefinitions[$key]['label'] = array(
+        'type' => 'string',
+        'label' => t('Label (auto-create)'),
+        'computed' => TRUE,
+      );
+      static::$propertyDefinitions[$key]['access'] = array(
+        'type' => 'boolean',
+        'label' => t('Access'),
+        'computed' => TRUE,
       );
     }
-
-    return $schema;
-  }
-
-  /**
-   * {@inheritdoc}
-   */
-  public function preSave() {
-    $entity = $this->get('entity')->getValue();
-    $target_id = $this->get('target_id')->getValue();
-
-    if (empty($target_id) && !empty($entity) && $entity->isNew()) {
-      $entity->save();
-      $this->set('target_id', $entity->id());
-    }
+    return static::$propertyDefinitions[$key];
   }
 
   /**
diff --git a/core/modules/field/lib/Drupal/field/Plugin/Type/FieldType/ConfigEntityReferenceItemBase.php b/core/modules/field/lib/Drupal/field/Plugin/Type/FieldType/ConfigEntityReferenceItemBase.php
deleted file mode 100644
index 6b3c137..0000000
--- a/core/modules/field/lib/Drupal/field/Plugin/Type/FieldType/ConfigEntityReferenceItemBase.php
+++ /dev/null
@@ -1,175 +0,0 @@
-<?php
-
-/**
- * @file
- * Contains \Drupal\field\Plugin\Type\FieldType\ConfigEntityReferenceItemBase.
- */
-
-namespace Drupal\field\Plugin\Type\FieldType;
-
-use Drupal\Core\Entity\Plugin\DataType\EntityReferenceItem;
-use Drupal\field\Plugin\Type\FieldType\ConfigFieldItemInterface;
-use Drupal\field\FieldInterface;
-use Drupal\field\FieldInstanceInterface;
-
-/**
- * A common base class for configurable entity reference fields.
- *
- * Extends the Core 'entity_reference' entity field item with properties for
- * revision ids, labels (for autocreate) and access.
- *
- * Required settings (below the definition's 'settings' key) are:
- *  - target_type: The entity type to reference.
- */
-class ConfigEntityReferenceItemBase extends EntityReferenceItem implements ConfigFieldItemInterface {
-
-  /**
-   * Definitions of the contained properties.
-   *
-   * @see ConfigurableEntityReferenceItem::getPropertyDefinitions()
-   *
-   * @var array
-   */
-  static $propertyDefinitions;
-
-  /**
-   * {@inheritdoc}
-   */
-  public function getPropertyDefinitions() {
-    // Definitions vary by entity type and bundle, so key them accordingly.
-    $key = $this->definition['settings']['target_type'] . ':';
-    $key .= isset($this->definition['settings']['target_bundle']) ? $this->definition['settings']['target_bundle'] : '';
-
-    if (!isset(static::$propertyDefinitions[$key])) {
-      // Call the parent to define the target_id and entity properties.
-      parent::getPropertyDefinitions();
-
-      static::$propertyDefinitions[$key]['revision_id'] = array(
-        // @todo: Lookup the entity type's ID data type and use it here.
-        'type' => 'integer',
-        'label' => t('Revision ID'),
-        'constraints' => array(
-          'Range' => array('min' => 0),
-        ),
-      );
-      static::$propertyDefinitions[$key]['label'] = array(
-        'type' => 'string',
-        'label' => t('Label (auto-create)'),
-        'computed' => TRUE,
-      );
-      static::$propertyDefinitions[$key]['access'] = array(
-        'type' => 'boolean',
-        'label' => t('Access'),
-        'computed' => TRUE,
-      );
-    }
-    return static::$propertyDefinitions[$key];
-  }
-
-  /**
-   * {@inheritdoc}
-   *
-   * Copied from \Drupal\field\Plugin\field\field_type\LegacyConfigFieldItem,
-   * since we cannot extend it.
-   */
-  public static function schema(FieldInterface $field) {
-    $definition = \Drupal::service('plugin.manager.entity.field.field_type')->getDefinition($field->type);
-    $module = $definition['provider'];
-    module_load_install($module);
-    $callback = "{$module}_field_schema";
-    if (function_exists($callback)) {
-      return $callback($field);
-    }
-  }
-
-  /**
-   * {@inheritdoc}
-   */
-  public function isEmpty() {
-    // Avoid loading the entity by first checking the 'target_id'.
-    $target_id = $this->get('target_id')->getValue();
-    if (!empty($target_id) && is_numeric($target_id)) {
-      return FALSE;
-    }
-    // Allow auto-create entities.
-    if (empty($target_id) && ($entity = $this->get('entity')->getValue()) && $entity->isNew()) {
-      return FALSE;
-    }
-    return TRUE;
-  }
-
-  /**
-   * {@inheritdoc}
-   *
-   * Copied from \Drupal\field\Plugin\field\field_type\LegacyConfigFieldItem,
-   * since we cannot extend it.
-   */
-  public function settingsForm(array $form, array &$form_state, $has_data) {
-    if ($callback = $this->getLegacyCallback('settings_form')) {
-      $instance = $this->getFieldDefinition();
-      if (!($instance instanceof FieldInstanceInterface)) {
-        throw new \UnexpectedValueException('ConfigEntityReferenceItemBase::settingsForm() called for a field whose definition is not a field instance.');
-      }
-      // hook_field_settings_form() used to receive the $instance (not actually
-      // needed), and the value of field_has_data().
-      return $callback($instance->getField(), $instance, $has_data);
-    }
-    return array();
-  }
-
-  /**
-   * {@inheritdoc}
-   *
-   * Copied from \Drupal\field\Plugin\field\field_type\LegacyConfigFieldItem,
-   * since we cannot extend it.
-   */
-  public function instanceSettingsForm(array $form, array &$form_state) {
-    if ($callback = $this->getLegacyCallback('instance_settings_form')) {
-      $instance = $this->getFieldDefinition();
-      if (!($instance instanceof FieldInstanceInterface)) {
-        throw new \UnexpectedValueException('ConfigEntityReferenceItemBase::instanceSettingsForm() called for a field whose definition is not a field instance.');
-      }
-      return $callback($instance->getField(), $instance, $form_state);
-    }
-    return array();
-  }
-
-  /**
-   * Returns options provided via the legacy callback hook_options_list().
-   *
-   * @todo: Convert all legacy callback implementations to methods.
-   *
-   * @see \Drupal\Core\TypedData\AllowedValuesInterface
-   */
-  public function getSettableOptions() {
-    $definition = $this->getPluginDefinition();
-    $callback = "{$definition['provider']}_options_list";
-    if (function_exists($callback)) {
-      // We are at the field item level, so we need to go two levels up to get
-      // to the entity object.
-      return $callback($this->getFieldDefinition(), $this->getEntity());
-    }
-  }
-
-  /**
-   * Returns the legacy callback for a given field type "hook".
-   *
-   * Copied from \Drupal\field\Plugin\field\field_type\LegacyConfigFieldItem,
-   * since we cannot extend it.
-   *
-   * @param string $hook
-   *   The name of the hook, e.g. 'settings_form', 'is_empty'.
-   *
-   * @return string|null
-   *   The name of the legacy callback, or NULL if it does not exist.
-   */
-  protected function getLegacyCallback($hook) {
-    $definition = $this->getPluginDefinition();
-    $module = $definition['provider'];
-    $callback = "{$module}_field_{$hook}";
-    if (function_exists($callback)) {
-      return $callback;
-    }
-  }
-
-}
diff --git a/core/modules/file/lib/Drupal/file/Plugin/field/field_type/FileItem.php b/core/modules/file/lib/Drupal/file/Plugin/field/field_type/FileItem.php
index 5de9a76..11e4911 100644
--- a/core/modules/file/lib/Drupal/file/Plugin/field/field_type/FileItem.php
+++ b/core/modules/file/lib/Drupal/file/Plugin/field/field_type/FileItem.php
@@ -11,7 +11,6 @@
 use Drupal\Core\Entity\Annotation\FieldType;
 use Drupal\Core\Entity\Plugin\DataType\EntityReferenceItem;
 use Drupal\field\FieldInterface;
-use Drupal\field\Plugin\Type\FieldType\ConfigFieldItemInterface;
 
 /**
  * Plugin implementation of the 'file' field type.
@@ -36,7 +35,7 @@
  *   list_class = "\Drupal\file\Plugin\field\field_type\FileField"
  * )
  */
-class FileItem extends EntityReferenceItem implements ConfigFieldItemInterface {
+class FileItem extends EntityReferenceItem {
 
   /**
    * Property definitions of the contained properties.
@@ -213,6 +212,13 @@ public function instanceSettingsForm(array $form, array &$form_state) {
   /**
    * {@inheritdoc}
    */
+  public function preSave() {
+    return;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
   public function insert() {
     // @todo Move in FileField in https://drupal.org/node/2073033.
     $entity = $this->getRoot();
diff --git a/core/modules/taxonomy/lib/Drupal/taxonomy/Plugin/field/field_type/TaxonomyTermReferenceItem.php b/core/modules/taxonomy/lib/Drupal/taxonomy/Plugin/field/field_type/TaxonomyTermReferenceItem.php
index 3997007..a2bdd38 100644
--- a/core/modules/taxonomy/lib/Drupal/taxonomy/Plugin/field/field_type/TaxonomyTermReferenceItem.php
+++ b/core/modules/taxonomy/lib/Drupal/taxonomy/Plugin/field/field_type/TaxonomyTermReferenceItem.php
@@ -11,7 +11,6 @@
 use Drupal\Core\Annotation\Translation;
 use Drupal\field\FieldInterface;
 use Drupal\Core\Entity\Plugin\DataType\EntityReferenceItem;
-use Drupal\field\Plugin\Type\FieldType\ConfigFieldItemInterface;
 use Drupal\Core\Session\AccountInterface;
 use Drupal\Core\TypedData\AllowedValuesInterface;
 
@@ -36,7 +35,7 @@
  *   default_formatter = "taxonomy_term_reference_link"
  * )
  */
-class TaxonomyTermReferenceItem extends EntityReferenceItem implements ConfigFieldItemInterface, AllowedValuesInterface {
+class TaxonomyTermReferenceItem extends EntityReferenceItem implements AllowedValuesInterface {
 
   /**
    * {@inheritdoc}
@@ -86,30 +85,6 @@ public function getPropertyDefinitions() {
   /**
    * {@inheritdoc}
    */
-  public static function schema(FieldInterface $field) {
-    return array(
-      'columns' => array(
-        'target_id' => array(
-          'type' => 'int',
-          'unsigned' => TRUE,
-          'not null' => FALSE,
-        ),
-      ),
-      'indexes' => array(
-        'target_id' => array('target_id'),
-      ),
-      'foreign keys' => array(
-        'target_id' => array(
-          'table' => 'taxonomy_term_data',
-          'columns' => array('target_id' => 'tid'),
-        ),
-      ),
-    );
-  }
-
-  /**
-   * {@inheritdoc}
-   */
   public function settingsForm(array $form, array &$form_state, $has_data) {
     // Get proper values for 'allowed_values_function', which is a core setting.
     $vocabularies = entity_load_multiple('taxonomy_vocabulary');
@@ -144,29 +119,25 @@ public function settingsForm(array $form, array &$form_state, $has_data) {
   /**
    * {@inheritdoc}
    */
-  public function instanceSettingsForm(array $form, array &$form_state) {
-    return;
-  }
-
-  /**
-   * {@inheritdoc}
-   */
-  public function isEmpty() {
-    $target_id = $this->get('target_id')->getValue();
-    $entity = $this->get('entity')->getValue();
-    return (empty($target_id) && empty($entity));
-  }
-
-  /**
-   * {@inheritdoc}
-   */
-  public function preSave() {
-    $target_id = $this->get('target_id')->getValue();
-    $entity = $this->get('entity')->getValue();
-    if (!$target_id) {
-      $this->entity = $entity->save();
-      $this->target_id = $entity->id();
-    }
+  public static function schema(FieldInterface $field) {
+    return array(
+      'columns' => array(
+        'target_id' => array(
+          'type' => 'int',
+          'unsigned' => TRUE,
+          'not null' => FALSE,
+        ),
+      ),
+      'indexes' => array(
+        'target_id' => array('target_id'),
+      ),
+      'foreign keys' => array(
+        'target_id' => array(
+          'table' => 'taxonomy_term_data',
+          'columns' => array('target_id' => 'tid'),
+        ),
+      ),
+    );
   }
 
   /**