diff --git a/core/modules/file/file.module b/core/modules/file/file.module
index de76bb4..efd4afb 100644
--- a/core/modules/file/file.module
+++ b/core/modules/file/file.module
@@ -1116,9 +1116,10 @@ function file_managed_file_submit($form, FormStateInterface $form_state) {
   $element = NestedArray::getValue($form, $parents);
 
   // No action is needed here for the upload button, because all file uploads on
-  // the form are processed by file_managed_file_value() regardless of which
-  // button was clicked. Action is needed here for the remove button, because we
-  // only remove a file in response to its remove button being clicked.
+  // the form are processed by \Drupal\file\Element\ManagedFile::valueCallback()
+  // regardless of which button was clicked. Action is needed here for the
+  // remove button, because we only remove a file in response to its remove
+  // button being clicked.
   if ($button_key == 'remove_button') {
     $fids = array_keys($element['#files']);
     // Get files that will be removed.
@@ -1152,8 +1153,9 @@ function file_managed_file_submit($form, FormStateInterface $form_state) {
     // $form_state->getValues() must be updated in case additional submit
     // handlers run, and for form building functions that run during the
     // rebuild, such as when the managed_file element is part of a field widget.
-    // FormState::$input must be updated so that file_managed_file_value()
-    // has correct information during the rebuild.
+    // FormState::$input must be updated so that
+    // \Drupal\file\Element\ManagedFile::valueCallback() has correct information
+    // during the rebuild.
     form_set_value($element['fids'], implode(' ', $fids), $form_state);
     NestedArray::setValue($form_state->getUserInput(), $element['fids']['#parents'], implode(' ', $fids));
   }
diff --git a/core/modules/file/src/Element/ManagedFile.php b/core/modules/file/src/Element/ManagedFile.php
index 14d1dd8..f5a442c 100644
--- a/core/modules/file/src/Element/ManagedFile.php
+++ b/core/modules/file/src/Element/ManagedFile.php
@@ -203,8 +203,8 @@ public static function processManagedFile(&$element, FormStateInterface $form_st
           '#type' => 'hidden',
           '#value' => $upload_progress_key,
           '#attributes' => array('class' => array('file-progress')),
-          // Uploadprogress extension requires this field to be at the top of the
-          // form.
+          // Uploadprogress extension requires this field to be at the top of
+          // the form.
           '#weight' => -20,
         );
       }
@@ -213,8 +213,8 @@ public static function processManagedFile(&$element, FormStateInterface $form_st
           '#type' => 'hidden',
           '#value' => $upload_progress_key,
           '#attributes' => array('class' => array('file-progress')),
-          // Uploadprogress extension requires this field to be at the top of the
-          // form.
+          // Uploadprogress extension requires this field to be at the top of
+          // the form.
           '#weight' => -20,
         );
       }
@@ -276,16 +276,16 @@ public static function processManagedFile(&$element, FormStateInterface $form_st
    *
    * Upload controls are hidden when a file is already uploaded. Remove controls
    * are hidden when there is no file attached. Controls are hidden here instead
-   * of in file_managed_file_process(), because #access for these buttons depends
-   * on the managed_file element's #value. See the documentation of form_builder()
-   * for more detailed information about the relationship between #process,
-   * #value, and #access.
+   * of in file_managed_file_process(), because #access for these buttons
+   * depends on the managed_file element's #value. See the documentation of
+   * form_builder() for more detailed information about the relationship between
+   * #process, #value, and #access.
    *
    * Because #access is set here, it affects display only and does not prevent
-   * JavaScript or other untrusted code from submitting the form as though access
-   * were enabled. The form processing functions for these elements should not
-   * assume that the buttons can't be "clicked" just because they are not
-   * displayed.
+   * JavaScript or other untrusted code from submitting the form as though
+   * access were enabled. The form processing functions for these elements
+   * should not assume that the buttons can't be "clicked" just because they are
+   * not displayed.
    */
   public static function preRenderManagedFile($element) {
     // If we already have a file, we don't want to show the upload controls.
@@ -315,7 +315,7 @@ public static function validateManagedFile(&$element, FormStateInterface $form_s
       foreach ($fids as $fid) {
         if ($file = File::load($fid)) {
           if ($file->isPermanent()) {
-            $references = \Drupal::service('file.usage')->listUsage($file);
+            $references = static::fileUsage()->listUsage($file);
             if (empty($references)) {
               $form_state->setError($element, t('The file used in the !name field may not be referenced.', array('!name' => $element['#title'])));
             }
@@ -338,4 +338,13 @@ public static function validateManagedFile(&$element, FormStateInterface $form_s
     }
   }
 
+  /**
+   * Wraps the file usage service.
+   *
+   * @return \Drupal\file\FileUsage\FileUsageInterface
+   */
+  protected static function fileUsage() {
+    return \Drupal::service('file.usage');
+  }
+
 }
diff --git a/core/modules/file/src/Plugin/Field/FieldWidget/FileWidget.php b/core/modules/file/src/Plugin/Field/FieldWidget/FileWidget.php
index f9becf4..ab0c6a8 100644
--- a/core/modules/file/src/Plugin/Field/FieldWidget/FileWidget.php
+++ b/core/modules/file/src/Plugin/Field/FieldWidget/FileWidget.php
@@ -14,6 +14,7 @@
 use Drupal\Core\Field\WidgetBase;
 use Drupal\Core\Form\FormStateInterface;
 use Drupal\Core\Render\Element;
+use Drupal\file\Element\ManagedFile;
 
 /**
  * Plugin implementation of the 'file_generic' widget.
@@ -289,7 +290,7 @@ public static function value($element, $input = FALSE, FormStateInterface $form_
     }
 
     // We depend on the managed file element to handle uploads.
-    $return = file_managed_file_value($element, $input, $form_state);
+    $return = ManagedFile::valueCallback($element, $input, $form_state);
 
     // Ensure that all the required properties are returned even if empty.
     $return += array(