Extract language settings methods into a LanguageHelper interface

chrome/browser/resources/settings/languages_page/languages_page.html

 <link rel="import" href="chrome://resources/polymer/v1_0/polymer/polymer.html">
 <link rel="import" href="chrome://resources/polymer/v1_0/iron-flex-layout/iron-flex-layout.html">
 <link rel="import" href="chrome://resources/polymer/v1_0/iron-icon/iron-icon.html">
 <link rel="import" href="chrome://resources/polymer/v1_0/iron-icons/iron-icons.html">
 <link rel="import" href="chrome://resources/polymer/v1_0/neon-animation/neon-animatable.html">
 <link rel="import" href="chrome://resources/polymer/v1_0/paper-button/paper-button.html">
 <link rel="import" href="chrome://resources/polymer/v1_0/paper-icon-button/paper-icon-button.html">
 <link rel="import" href="chrome://resources/polymer/v1_0/paper-item/paper-item.html">
 <link rel="import" href="chrome://resources/html/assert.html">
 <link rel="import" href="chrome://resources/html/cr.html">
 <link rel="import" href="chrome://md-settings/settings_page/settings_animated_pages.html">
 <link rel="import" href="chrome://md-settings/settings_page/settings_subheader.html">
 <link rel="import" href="language_detail_page.html">
 <link rel="import" href="languages.html">
 <link rel="import" href="manage_languages_page.html">
 
 <if expr="not is_macosx">
 <link rel="import" href="edit_dictionary_page.html">
 </if>
 
 <dom-module id="settings-languages-page">
   <link rel="import" type="css"
       href="chrome://md-settings/settings_page/settings_page.css">
   <link rel="import" type="css" href="languages_page.css">
   <template>
-    <settings-languages id="languages" languages="{{languages}}">
-    </settings-languages>
+    <settings-languages languages="{{languages}}"></settings-languages>
     <settings-animated-pages id="pages" current-route="{{currentRoute}}"
         section="languages">
       <neon-animatable id="main">
         <div class="settings-box">
           <h2 i18n-content="languagesListTitle"></h2>
           <div>
             <array-selector id="languageSelector" selected="{{detailLanguage}}"
                 items="{{languages.enabledLanguages}}"></array-selector>
             <template is="dom-repeat" items="{{languages.enabledLanguages}}">
               <paper-item class="split" on-tap="onLanguageTap_">
                 <div class="flex" title="[[item.language.nativeDisplayName]]"
                     >[[item.language.displayName]]</div>
+<if expr="chromeos or is_win">
                 <iron-icon icon="done"
-                    hidden$="[[!isUILanguage_(item.language.code, prefs.intl.app_locale.value)]]">
+                    hidden$="[[!isProspectiveUILanguage_(item.language.code, prefs.intl.app_locale.value)]]">
                 </iron-icon>
+</if>
                 <paper-icon-button icon="settings"
                     on-tap="onShowLanguageDetailTap_"></paper-icon-button>
               </paper-item>
             </template>
           </div>
           <div class="manage">
             <paper-button i18n-content="manageLanguages"
                 on-tap="onManageLanguagesTap_"></paper-button>
           </div>
 <if expr="chromeos">
@@ skipping 49 matching lines @@
         <settings-subheader id="edit-dictionary-subheader"
             i18n-values="page-title:editDictionaryPageTitle">
         </settings-subheader>
         <settings-edit-dictionary-page></settings-edit-dictionary-page>
       </neon-animatable>
 </if>
     </settings-animated-pages>
   </template>
   <script src="languages_page.js"></script>
 </dom-module>