diff -u b/core/modules/ckeditor/ckeditor.libraries.yml b/core/modules/ckeditor/ckeditor.libraries.yml
--- b/core/modules/ckeditor/ckeditor.libraries.yml
+++ b/core/modules/ckeditor/ckeditor.libraries.yml
@@ -78,9 +78,7 @@
   dependencies:
     - core/jquery
     - core/drupal
-    - core/jquery.once
     - core/drupal.vertical-tabs
-    - core/drupalSettings
     # Ensure to run after ckeditor/drupal.ckeditor.admin.
     - ckeditor/drupal.ckeditor.admin
 
diff -u b/core/modules/ckeditor/config/schema/ckeditor.schema.yml b/core/modules/ckeditor/config/schema/ckeditor.schema.yml
--- b/core/modules/ckeditor/config/schema/ckeditor.schema.yml
+++ b/core/modules/ckeditor/config/schema/ckeditor.schema.yml
@@ -38,9 +38,9 @@
   type: mapping
   label: 'Language'
   mapping:
-    list_type:
+    language_list_type:
       type: string
-      label: 'Language list ID'
+      label: 'Language list type ID'
 
 # Plugin \Drupal\ckeditor\Plugin\ckeditor\plugin\StylesCombo
 ckeditor.plugin.stylescombo:
diff -u b/core/modules/ckeditor/js/ckeditor.language.admin.js b/core/modules/ckeditor/js/ckeditor.language.admin.js
--- b/core/modules/ckeditor/js/ckeditor.language.admin.js
+++ b/core/modules/ckeditor/js/ckeditor.language.admin.js
@@ -8,7 +8,7 @@
   Drupal.behaviors.ckeditorLanguageSettingsSummary = {
     attach: function () {
       $('#edit-editor-settings-plugins-language').drupalSetSummary(function (context) {
-        return $('#edit-editor-settings-plugins-language-list-type option:selected').text();
+        return $('#edit-editor-settings-plugins-language-language-list-type option:selected').text();
       });
     }
   };
diff -u b/core/modules/ckeditor/src/Plugin/CKEditorPlugin/Language.php b/core/modules/ckeditor/src/Plugin/CKEditorPlugin/Language.php
--- b/core/modules/ckeditor/src/Plugin/CKEditorPlugin/Language.php
+++ b/core/modules/ckeditor/src/Plugin/CKEditorPlugin/Language.php
@@ -53,20 +53,20 @@
    * {@inheritdoc}
    */
   public function getConfig(Editor $editor) {
-    $language_list = array();
-    $config = array('list_type' => 'un');
+    $language_list = [];
+    $config = ['language_list_type' => 'un'];
     $settings = $editor->getSettings();
     if (isset($settings['plugins']['language'])) {
       $config = $settings['plugins']['language'];
     }
 
-    $predefined_languages = ($config['list_type'] == 'all') ?
+    $predefined_languages = ($config['language_list_type'] === 'all') ?
       LanguageManager::getStandardLanguageList() :
       LanguageManager::getUnitedNationsLanguageList();
 
-    // Generate the language_list setting as expected by the CKEditor
-    // Language plugin, but key the values by the full language name
-    // so that we can sort them later on.
+    // Generate the language_list setting as expected by the CKEditor Language
+    // plugin, but key the values by the full language name so that we can sort
+    // them later on.
     foreach ($predefined_languages as $langcode => $language) {
       $english_name = $language[0];
       $direction = empty($language[2]) ? NULL : $language[2];
@@ -80,9 +80,7 @@
 
     // Sort on full language name.
     ksort($language_list);
-    $config = array(
-      'language_list' => array_values($language_list),
-    );
+    $config = ['language_list' => array_values($language_list)];
     return $config;
   }
 
@@ -93,7 +91,10 @@
     return array(
       'Language' => array(
         'label' => $this->t('Language'),
-        'image_alternative' => '<a href="#" class="cke-icon-only cke_ltr" role="button" title="' . $this->t('Language') . '" aria-label="' . $this->t('Language') . '"><span class="cke_button_icon cke_button__language_icon">' . $this->t('Language') . '<span class="ckeditor-button-arrow"></span></span></a>',
+        'image_alternative' => [
+          '#type' => 'inline_template',
+          '#template' => '<a href="#" class="cke-icon-only" role="button" title="' . $this->t('Language') . '" aria-label="' . $this->t('Language') . '"><span class="cke_button_icon cke_button__language_icon">' . $this->t('Language') . '</span></a>',
+        ],
       ),
     );
   }
@@ -103,29 +104,27 @@
    */
   public function settingsForm(array $form, FormStateInterface $form_state, Editor $editor) {
     // Defaults.
-    $config = array('list_type' => 'un');
+    $config = ['language_list_type' => 'un'];
     $settings = $editor->getSettings();
     if (isset($settings['plugins']['language'])) {
       $config = $settings['plugins']['language'];
     }
 
     $predefined_languages = LanguageManager::getStandardLanguageList();
-    $form['list_type'] = array(
+    $form['language_list_type'] = array(
       '#title' => $this->t('Language list type'),
       '#title_display' => 'invisible',
       '#type' => 'select',
-      '#options' => array(
-        'un' => $this->t('United Nations subset'),
-        'all' => $this->t('All @count languages', array('@count' => sizeof($predefined_languages))),
-      ),
-      '#default_value' => $config['list_type'],
-      '#description' => $this->t('The list of languages to show in the language dropdown. The basic list will only show the <a href="@url">six official languages of the UN</a>. The extended list will show all @count languages that are available in Drupal.', array(
-        '@url' => Url::fromUri('http://www.un.org/en/aboutun/languages.shtml/')->toString(),
-        '@count' => sizeof($predefined_languages),
-      )),
-      '#attached' => array(
-        'library' => array('ckeditor/drupal.ckeditor.language.admin'),
-      ),
+      '#options' => [
+        'un' => $this->t("United Nations' official languages"),
+        'all' => $this->t('All @count languages', ['@count' => count($predefined_languages)]),
+      ],
+      '#default_value' => $config['language_list_type'],
+      '#description' => $this->t('The list of languages to show in the language dropdown. The basic list will only show the <a href=":url">six official languages of the UN</a>. The extended list will show all @count languages that are available in Drupal.', [
+        ':url' => Url::fromUri('http://www.un.org/en/aboutun/languages.shtml/')->toString(),
+        '@count' => count($predefined_languages),
+      ]),
+      '#attached' => ['library' => ['ckeditor/drupal.ckeditor.language.admin']],
     );
 
     return $form;
diff -u b/core/modules/ckeditor/src/Plugin/Editor/CKEditor.php b/core/modules/ckeditor/src/Plugin/Editor/CKEditor.php
--- b/core/modules/ckeditor/src/Plugin/Editor/CKEditor.php
+++ b/core/modules/ckeditor/src/Plugin/Editor/CKEditor.php
@@ -135,11 +135,7 @@
           ),
         ),
       ),
-      'plugins' => array(
-        'language' => array(
-          'list_type' => 'un',
-        ),
-      ),
+      'plugins' => ['language' => ['language_list_type' => 'un']],
     );
   }
 
diff -u b/core/modules/ckeditor/src/Tests/CKEditorAdminTest.php b/core/modules/ckeditor/src/Tests/CKEditorAdminTest.php
--- b/core/modules/ckeditor/src/Tests/CKEditorAdminTest.php
+++ b/core/modules/ckeditor/src/Tests/CKEditorAdminTest.php
@@ -109,11 +109,7 @@
           ),
         ),
       ),
-      'plugins' => array(
-        'language' => array(
-          'list_type' => 'un',
-        ),
-      ),
+      'plugins' => ['language' => ['language_list_type' => 'un']],
     );
     $this->assertIdentical($this->castSafeStrings($ckeditor->getDefaultSettings()), $expected_default_settings);
 
diff -u b/core/modules/ckeditor/tests/src/Unit/Plugin/CKEditorPlugin/LanguageTest.php b/core/modules/ckeditor/tests/src/Unit/Plugin/CKEditorPlugin/LanguageTest.php
--- b/core/modules/ckeditor/tests/src/Unit/Plugin/CKEditorPlugin/LanguageTest.php
+++ b/core/modules/ckeditor/tests/src/Unit/Plugin/CKEditorPlugin/LanguageTest.php
@@ -23,7 +23,7 @@
    * {@inheritdoc}
    */
   public function setUp() {
-    $this->plugin = new Language(array(), $this->randomMachineName(), array());
+    $this->plugin = new Language([], $this->randomMachineName(), []);
   }
 
   /**
@@ -41,13 +41,13 @@
    *
    * @dataProvider providerGetConfig
    */
-  public function testGetConfig($list_type, $expected_number) {
+  public function testGetConfig($language_list_type, $expected_number) {
     $editor = $this->getMockBuilder('Drupal\editor\Entity\Editor')
       ->disableOriginalConstructor()
       ->getMock();
     $editor->expects($this->once())
       ->method('getSettings')
-      ->willReturn(['plugins' => ['language' => ['list_type' => $list_type]]]);
+      ->willReturn(['plugins' => ['language' => ['language_list_type' => $language_list_type]]]);
 
     $config = $this->plugin->getConfig($editor);
 
only in patch2:
unchanged:
--- a/core/lib/Drupal/Core/Language/Language.php
+++ b/core/lib/Drupal/Core/Language/Language.php
@@ -21,13 +21,13 @@ class Language implements LanguageInterface {
    *
    * @var array
    */
-  public static $defaultValues = array(
+  public static $defaultValues = [
     'id' => 'en',
     'name' => 'English',
     'direction' => self::DIRECTION_LTR,
     'weight' => 0,
     'locked' => FALSE,
-  );
+  ];
 
   // Properties within the Language are set up as the default language.
 
@@ -79,7 +79,7 @@ class Language implements LanguageInterface {
    *   An array of property values, keyed by property name, used to construct
    *   the language.
    */
-  public function __construct(array $values = array()) {
+  public function __construct(array $values = []) {
     // Set all the provided properties for the language.
     foreach ($values as $key => $value) {
       if (property_exists($this, $key)) {