MD Settings: add empty list message for spell-check edit page.

chrome/test/data/webui/settings/fake_language_settings_private.js

 // Copyright 2016 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 /**
  * @fileoverview Fake implementation of chrome.languageSettingsPrivate
  * for testing.
  */
 cr.define('settings', function() {
   /**
@@ skipping 154 matching lines @@
      *     !chrome.languageSettingsPrivate.SpellcheckDictionaryStatus>):void}
      *     callback
      */
     getSpellcheckDictionaryStatuses:
         wrapAssertNotReached('getSpellcheckDictionaryStatuses'),
 
     /**
      * Gets the custom spell check words, in sorted order.
      * @param {function(!Array<string>):void} callback
      */
-    getSpellcheckWords: wrapAssertNotReached('getSpellcheckWords'),
+    getSpellcheckWords: function(callback) {
+      callback([]);
+    },
 
     /**
      * Adds a word to the custom dictionary.
      * @param {string} word
      */
-    addSpellcheckWord: wrapAssertNotReached('addSpellcheckWord'),
+    addSpellcheckWord: function(word) {
+      // Current tests don't actually care about this implementation.
+    },
 
     /**
      * Removes a word from the custom dictionary.
      * @param {string} word
      */
     removeSpellcheckWord: wrapAssertNotReached('removeSpellcheckWord'),
 
     /**
      * Gets the translate target language (in most cases, the display locale).
      * @param {function(string):void} callback
@@ skipping 76 matching lines @@
 
     /**
      * Called when an input method is removed.
      * @type {!ChromeEvent}
      */
     onInputMethodRemoved: new FakeChromeEvent(),
   };
 
   return {FakeLanguageSettingsPrivate: FakeLanguageSettingsPrivate};
 });