Implement chrome.languageSettingsPrivate custom spell check functions

chrome/common/extensions/api/language_settings_private.idl

 // Copyright 2015 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.
 
 // Use the <code>chrome.languageSettingsPrivate</code> API to get or change
 // language and input method settings.
 namespace languageSettingsPrivate {
   dictionary Language {
     // The unique code identifying the language.
     DOMString code;
@@ skipping 70 matching lines @@
     static void getLanguageList(GetLanguageListCallback callback);
 
     // Sets the accepted languages, used to decide which languages to translate,
     // generate the Accept-Language header, etc.
     static void setLanguageList(DOMString[] languageCodes);
 
     // Gets the current status of the chosen spell check dictionaries.
     static void getSpellcheckDictionaryStatuses(
         GetSpellcheckDictionaryStatusesCallback callback);
 
-    // Gets the custom spell check words.
+    // Gets the custom spell check words, in sorted order.
     static void getSpellcheckWords(GetSpellcheckWordsCallback callback);
 
+    // Adds a word to the custom dictionary.
+    static void addSpellcheckWord(DOMString word);
+
+    // Removes a word from the custom dictionary.
+    static void removeSpellcheckWord(DOMString word);
+
     // Gets the translate target language (in most cases, the display locale).
     static void getTranslateTargetLanguage(
         GetTranslateTargetLanguageCallback callback);
 
     // Gets all supported input methods, including IMEs. Chrome OS only.
     static void getInputMethodLists(GetInputMethodListsCallback callback);
 
     // Adds the input method to the current user's list of enabled input
     // methods, enabling the input method for the current user. Chrome OS only.
     static void addInputMethod(DOMString inputMethodId);
@@ skipping 14 matching lines @@
     static void onCustomDictionaryChanged(
         DOMString[] wordsAdded, DOMString[] wordsRemoved);
 
     // Called when an input method is added.
     static void onInputMethodAdded(DOMString inputMethodId);
 
     // Called when an input method is removed.
     static void onInputMethodRemoved(DOMString inputMethodId);
   };
 };