Update to Drupal 8.0.1. For more information, see https://www.drupal.org/node/2627402

core/modules/editor/js/editor.formattedTextEditor.js

@@ -122,9 +122,9 @@
           break;
 
         case 'activating':
-          // When transformation filters have been been applied to the formatted
-          // text of this field, then we'll need to load a re-formatted version
-          // of it without the transformation filters.
+          // When transformation filters have been applied to the formatted text
+          // of this field, then we'll need to load a re-formatted version of it
+          // without the transformation filters.
           if (this.textFormatHasTransformations) {
             var $textElement = this.$textElement;
             this._getUntransformedText(function (untransformedText) {

core/modules/editor/src/EditorController.php

@@ -28,7 +28,7 @@ class EditorController extends ControllerBase {
    * @param \Drupal\Core\Entity\EntityInterface $entity
    *   The entity of which a formatted text field is being rerendered.
    * @param string $field_name
-   *   The name of the (formatted text) field that that is being rerendered
+   *   The name of the (formatted text) field that is being rerendered
    * @param string $langcode
    *   The name of the language for which the formatted text field is being
    *   rerendered.

core/modules/editor/src/Element.php

@@ -18,7 +18,7 @@ use Drupal\Core\Render\BubbleableMetadata;
 class Element {
 
   /**
-   * The Text Editor plugin manager manager service.
+   * The Text Editor plugin manager service.
    *
    * @var \Drupal\Component\Plugin\PluginManagerInterface
    */