Issue #3431657: Replace the "displayfields.token" service with a protected class method

Closes #3431657

src/Plugin/DisplayFieldsField/FieldExtraField.php

@@ -72,7 +72,7 @@ public function createForm($form, FormStateInterface $form_state, $parents = [])
     ];
 
     // Add the token browser at the bottom.
-    $form['token'] = \Drupal::service('displayfields.token')->tokenBrowser();
+    $form['token'] = $this->tokenBrowser();
 
     return $form;
   }
@@ -217,10 +217,37 @@ protected function fieldRowSettingsForm($form, FormStateInterface $form_state, $
       '#default_value' => $data,
     ];
     // Add the token browser at the top.
-    $elements['token'] = \Drupal::service('displayfields.token')->tokenBrowser();
+    $elements['token'] = $this->tokenBrowser();
     return $elements;
   }
 
+  /**
+   * Gets the token browser.
+   *
+   * @return array
+   *   The render array for the token browser, if the Token module is
+   *   installed, or for a short description about how to use tokens.
+   */
+  protected function tokenBrowser() {
+    $element['intro_text'] = [
+      '#markup' => '<p>' . t("Configure the tokens below. Use tokens to avoid redundant meta data and search engine penalization. For example, a 'keyword' value of 'example' will be shown on all content using this configuration, whereas using the [node:field_keywords] automatically inserts the 'keywords' values from the node.") . '</p>',
+    ];
+
+    if (\Drupal::moduleHandler()->moduleExists('token')) {
+      $element['tokens'] = [
+        '#theme' => 'token_tree_link',
+        '#token_types' => 'all',
+        '#global_types' => TRUE,
+        '#click_insert' => TRUE,
+        '#show_restricted' => FALSE,
+        '#recursion_limit' => 3,
+        '#text' => t('Browse available tokens'),
+      ];
+    }
+
+    return $element;
+  }
+
   /**
    * Builds the field row settings summary markup.
    *
@@ -408,7 +435,7 @@ public function getFieldBuild($entities, $display_field, $display_settings, $par
 
   /**
    * Gets the current view mode from the current display.
-   * 
+   *
    * @return string
    */
   protected function getCurrentViewMode() {