Add 'en' in addition to 'en-US' as Accept-Language.

chrome/browser/resources/options/chromeos_language_list.js

 // Copyright (c) 2010 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.
 
 cr.define('options.language', function() {
   const ArrayDataModel = cr.ui.ArrayDataModel;
   const LanguageOptions = options.LanguageOptions;
   const List = cr.ui.List;
   const ListItem = cr.ui.ListItem;
   const ListSingleSelectionModel = cr.ui.ListSingleSelectionModel;
@@ skipping 270 matching lines @@
       }
     },
 
     /**
      * Saves the preference.
      */
     savePreference_: function() {
       // Encode the language codes into a CSV string.
       Preferences.setStringPref(this.preferredLanguagesPref,
                                 this.dataModel.slice().join(','));
-      // Save the same language list as accept languages preference. In
-      // theory, we don't need two separate preferences but we keep these
-      // separate, as these are conceptually different. In other words,
-      // using "intl.accept_languages" for preferred languages in Chrome
-      // OS is a bit awkward.
+      // Save the same language list as accept languages preference as
+      // well, but we need to expand the language list, to make it more
+      // acceptable. For instance, some web sites don't understand 'en-US'
+      // but 'en'. See crosbug.com/9884.
+      var acceptLanguages = this.expandLanguageCodes(this.dataModel.slice());
       Preferences.setStringPref(this.acceptLanguagesPref,
-                                this.dataModel.slice().join(','));
+                                acceptLanguages.join(','));
       cr.dispatchSimpleEvent(this, 'save');
     },
 
     /**
+     * Expands language codes to make these more suitable for Accept-Language.
+     * Example: ['en-US', 'ja', 'en-CA'] => ['en-US', 'en', 'ja', 'en-CA'].
+     * 'en' won't appear twice as this function eliminates duplicates.
+     * @param {Array} languageCodes List of language codes.
+     * @private
+     */
+    expandLanguageCodes: function(languageCodes) {
+      var expandedLanguageCodes = [];
+      var seen = {};  // Used to eliminiate duplicates.
+      for (var i = 0; i < languageCodes.length; i++) {
+        var languageCode = languageCodes[i];
+        if (!(languageCode in seen)) {
+          expandedLanguageCodes.push(languageCode);
+          seen[languageCode] = true;
+        }
+        var parts = languageCode.split('-');
+        if (!(parts[0] in seen)) {
+          expandedLanguageCodes.push(parts[0]);
+          seen[parts[0]] = true;
+        }
+      }
+      return expandedLanguageCodes;
+    },
+
+    /**
      * Filters bad language codes in case bad language codes are
      * stored in the preference. Removes duplicates as well.
      * @param {Array} languageCodes List of language codes.
      * @private
      */
     filterBadLanguageCodes_: function(languageCodes) {
       var filteredLanguageCodes = [];
       var seen = {};
       for (var i = 0; i < languageCodes.length; i++) {
         // Check if the the language code is valid, and not
         // duplicate. Otherwise, skip it.
         if (LanguageList.isValidLanguageCode(languageCodes[i]) &&
             !(languageCodes[i] in seen)) {
           filteredLanguageCodes.push(languageCodes[i]);
           seen[languageCodes[i]] = true;
         }
       }
       return filteredLanguageCodes;
     },
   };
 
   return {
     LanguageList: LanguageList
   };
 });