Modify languageSettingsPrivate IDL and flesh out stub implementation

extensions/browser/extension_event_histogram_value.h

 // 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.
 
 #ifndef EXTENSIONS_BROWSER_EXTENSION_EVENT_HISTOGRAM_VALUE_H_
 #define EXTENSIONS_BROWSER_EXTENSION_EVENT_HISTOGRAM_VALUE_H_
 
 namespace extensions {
 namespace events {
 
@@ skipping 346 matching lines @@
   DIAL_ON_DEVICE_LIST,
   DIAL_ON_ERROR,
   CAST_CHANNEL_ON_MESSAGE,
   CAST_CHANNEL_ON_ERROR,
   SCREENLOCK_PRIVATE_ON_CHANGED,
   SCREENLOCK_PRIVATE_ON_AUTH_ATTEMPTED,
   TYPES_CHROME_SETTING_ON_CHANGE,
   TYPES_PRIVATE_CHROME_DIRECT_SETTING_ON_CHANGE,
   WEB_VIEW_INTERNAL_ON_MESSAGE,  // TODO(kalman): where are the rest of the
                                  // webview events?
+  LANGUAGE_SETTINGS_PRIVATE_ON_INPUT_METHOD_ADDED,
+  LANGUAGE_SETTINGS_PRIVATE_ON_INPUT_METHOD_REMOVED,
+  LANGUAGE_SETTINGS_PRIVATE_ON_SPELLCHECK_DICTIONARIES_CHANGED,
+  LANGUAGE_SETTINGS_PRIVATE_ON_CUSTOM_DICTIONARY_CHANGED,
   // Last entry: Add new entries above, then run:
   // python tools/metrics/histograms/update_extension_histograms.py
   ENUM_BOUNDARY
 };
 
 }  // namespace events
 }  // namespace extensions
 
 #endif  // EXTENSIONS_BROWSER_EXTENSION_EVENT_HISTOGRAM_VALUE_H_