Issue #1919322 by plach: Entity_load_unchanged() should be part of the storage controller.

core/includes/entity.inc

@@ -297,10 +297,9 @@ function entity_load_multiple_by_properties($entity_type, array $values) {
  *   The unchanged entity, or FALSE if the entity cannot be loaded.
  */
 function entity_load_unchanged($entity_type, $id) {
-  $controller = drupal_container()->get('plugin.manager.entity')->getStorageController($entity_type);
-  $controller->resetCache(array($id));
-  $result = $controller->load(array($id));
-  return reset($result);
+  return drupal_container()->get('plugin.manager.entity')
+    ->getStorageController($entity_type)
+    ->loadUnchanged($id);
 }
 
 /**

core/lib/Drupal/Core/Config/Entity/ConfigStorageController.php

@@ -142,6 +142,15 @@ class ConfigStorageController implements EntityStorageControllerInterface {
     return $entities;
   }
 
+  /**
+   * Implements \Drupal\Core\Entity\EntityStorageControllerInterface::loadUnchanged()
+   */
+  public function loadUnchanged($id) {
+    $this->resetCache(array($id));
+    $result = $this->load(array($id));
+    return reset($result);
+  }
+
   /**
    * Implements Drupal\Core\Entity\EntityStorageControllerInterface::loadRevision().
    */

core/lib/Drupal/Core/Entity/DatabaseStorageController.php

@@ -235,6 +235,15 @@ class DatabaseStorageController implements EntityStorageControllerInterface {
     return $entities;
   }
 
+  /**
+   * Implements \Drupal\Core\Entity\EntityStorageControllerInterface::loadUnchanged()
+   */
+  public function loadUnchanged($id) {
+    $this->resetCache(array($id));
+    $result = $this->load(array($id));
+    return reset($result);
+  }
+
   /**
    * Implements \Drupal\Core\Entity\EntityStorageControllerInterface::loadRevision().
    */

core/lib/Drupal/Core/Entity/EntityStorageControllerInterface.php

@@ -40,6 +40,20 @@ interface EntityStorageControllerInterface {
    */
   public function load(array $ids = NULL);
 
+  /**
+   * Loads an unchanged entity from the database.
+   *
+   * @param mixed $id
+   *   The ID of the entity to load.
+   *
+   * @return \Drupal\Core\Entity\EntityInterface
+   *   The unchanged entity, or FALSE if the entity cannot be loaded.
+   *
+   * @todo Remove this method once we have a reliable way to retrieve the
+   *   unchanged entity from the entity object.
+   */
+  public function loadUnchanged($id);
+
   /**
    * Load a specific entity revision.
    *