Extract language settings methods into a LanguageHelper interface

chrome/browser/resources/settings/languages_page/compiled_resources.gyp

 # 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.
 {
   'targets': [
     {
       'target_name': 'languages',
       'variables': {
         'depends': [
           '../prefs/prefs_types.js',
           '../prefs/compiled_resources.gyp:prefs',
           '../../../../../ui/webui/resources/js/compiled_resources.gyp:assert',
           '../../../../../ui/webui/resources/js/compiled_resources.gyp:cr',
+          'languages_types.js',
         ],
         'externs': [
           '<(EXTERNS_DIR)/chrome_send.js',
           '<(EXTERNS_DIR)/language_settings_private.js',
         ],
       },
       'includes': ['../../../../../third_party/closure_compiler/compile_js.gypi'],
     },
     {
       'target_name': 'language_detail_page',
       'variables': {
         'depends': [
           '../../../../../ui/webui/resources/cr_elements/policy/compiled_resources.gyp:cr_policy_indicator_behavior',
           '../../../../../ui/webui/resources/js/chromeos/compiled_resources.gyp:ui_account_tweaks',
           '../../../../../ui/webui/resources/js/compiled_resources.gyp:load_time_data',
           '../prefs/compiled_resources.gyp:prefs',
+          'languages_types.js',
           'languages.js',
         ],
         'externs': [
           '<(EXTERNS_DIR)/language_settings_private.js',
         ],
       },
       'includes': ['../../../../../third_party/closure_compiler/compile_js.gypi'],
     },
     {
       'target_name': 'languages_page',
       'variables': {
         'depends': [
           '../../../../../ui/webui/resources/js/compiled_resources.gyp:assert',
           '../../../../../ui/webui/resources/js/compiled_resources.gyp:cr',
           '../../../../../ui/webui/resources/js/compiled_resources.gyp:load_time_data',
           '../settings_page/settings_animated_pages.js',
           '../prefs/prefs_types.js',
           '../prefs/compiled_resources.gyp:prefs',
+          'languages_types.js',
           'languages.js',
         ],
         'externs': [
           '<(EXTERNS_DIR)/language_settings_private.js',
         ],
       },
       'includes': ['../../../../../third_party/closure_compiler/compile_js.gypi'],
     },
     {
       'target_name': 'manage_languages_page',
       'variables': {
         'depends': [
           '../../../../../ui/webui/resources/js/compiled_resources.gyp:assert',
           '../prefs/compiled_resources.gyp:prefs',
+          'languages_types.js',
           'languages.js',
         ],
         'externs': [
-          '../../../../../third_party/closure_compiler/externs/language_settings_private.js',
+          '<(EXTERNS_DIR)/language_settings_private.js',
         ],
       },
       'includes': ['../../../../../third_party/closure_compiler/compile_js.gypi'],
     },
   ],
 }