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

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

Index: chrome/test/data/webui/settings/fake_language_settings_private.js
diff --git a/chrome/test/data/webui/settings/fake_language_settings_private.js b/chrome/test/data/webui/settings/fake_language_settings_private.js
index 220cbfac13e9b4469ecbb8d74e3526b0cc3cc5c0..9baaa5600b2c73ae2416fbb93cca5df0f5c2ba8f 100644
--- a/chrome/test/data/webui/settings/fake_language_settings_private.js
+++ b/chrome/test/data/webui/settings/fake_language_settings_private.js
@@ -172,13 +172,17 @@ cr.define('settings', function() {
      * 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.