--- a/toolkit/modules/InlineSpellChecker.jsm
+++ b/toolkit/modules/InlineSpellChecker.jsm
@@ -1,16 +1,14 @@
 /* This Source Code Form is subject to the terms of the Mozilla Public
  * License, v. 2.0. If a copy of the MPL was not distributed with this
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
 var EXPORTED_SYMBOLS = [ "InlineSpellChecker",
                          "SpellCheckHelper" ];
-var gLanguageBundle;
-var gRegionBundle;
 const MAX_UNDO_STACK_DEPTH = 1;
 
 ChromeUtils.import("resource://gre/modules/Services.jsm");
 
 function InlineSpellChecker(aEditor) {
   this.init(aEditor);
   this.mAddedWordStack = []; // We init this here to preserve it between init/uninit calls
 }
@@ -165,19 +163,20 @@ InlineSpellChecker.prototype = {
     for (var i = 0; i < this.mSuggestionItems.length; i++) {
       this.mMenu.removeChild(this.mSuggestionItems[i]);
     }
     this.mSuggestionItems = [];
   },
 
   sortDictionaryList(list) {
     var sortedList = [];
+    var names = Services.intl.getLocaleDisplayNames(undefined, list);
     for (var i = 0; i < list.length; i++) {
       sortedList.push({"id": list[i],
-                       "label": this.getDictionaryDisplayName(list[i])});
+                       "label": names[i]});
     }
     sortedList.sort(function(a, b) {
       if (a.label < b.label)
         return -1;
       if (a.label > b.label)
         return 1;
       return 0;
     });
@@ -238,73 +237,16 @@ InlineSpellChecker.prototype = {
       if (insertBefore)
         menu.insertBefore(item, insertBefore);
       else
         menu.appendChild(item);
     }
     return list.length;
   },
 
-  // Formats a valid BCP 47 language tag based on available localized names.
-  getDictionaryDisplayName(dictionaryName) {
-    try {
-      // Get the display name for this dictionary.
-      let languageTagMatch = /^([a-z]{2,3}|[a-z]{4}|[a-z]{5,8})(?:[-_]([a-z]{4}))?(?:[-_]([A-Z]{2}|[0-9]{3}))?((?:[-_](?:[a-z0-9]{5,8}|[0-9][a-z0-9]{3}))*)(?:[-_][a-wy-z0-9](?:[-_][a-z0-9]{2,8})+)*(?:[-_]x(?:[-_][a-z0-9]{1,8})+)?$/i;
-      var [/* languageTag */, languageSubtag, scriptSubtag, regionSubtag, variantSubtags] = dictionaryName.match(languageTagMatch);
-    } catch (e) {
-      // If we weren't given a valid language tag, just use the raw dictionary name.
-      return dictionaryName;
-    }
-
-    if (!gLanguageBundle) {
-      // Create the bundles for language and region names.
-      gLanguageBundle = Services.strings.createBundle(
-          "chrome://global/locale/languageNames.properties");
-      gRegionBundle = Services.strings.createBundle(
-          "chrome://global/locale/regionNames.properties");
-    }
-
-    var displayName = "";
-
-    // Language subtag will normally be 2 or 3 letters, but could be up to 8.
-    try {
-      displayName += gLanguageBundle.GetStringFromName(languageSubtag.toLowerCase());
-    } catch (e) {
-      displayName += languageSubtag.toLowerCase(); // Fall back to raw language subtag.
-    }
-
-    // Region subtag will be 2 letters or 3 digits.
-    if (regionSubtag) {
-      displayName += " (";
-
-      try {
-        displayName += gRegionBundle.GetStringFromName(regionSubtag.toLowerCase());
-      } catch (e) {
-        displayName += regionSubtag.toUpperCase(); // Fall back to raw region subtag.
-      }
-
-      displayName += ")";
-    }
-
-    // Script subtag will be 4 letters.
-    if (scriptSubtag) {
-      displayName += " / ";
-
-      // XXX: See bug 666662 and bug 666731 for full implementation.
-      displayName += scriptSubtag; // Fall back to raw script subtag.
-    }
-
-    // Each variant subtag will be 4 to 8 chars.
-    if (variantSubtags)
-      // XXX: See bug 666662 and bug 666731 for full implementation.
-      displayName += " (" + variantSubtags.substr(1).split(/[-_]/).join(" / ") + ")"; // Collapse multiple variants.
-
-    return displayName;
-  },
-
   // undoes the work of addDictionaryListToMenu for the menu
   // (call on popup hiding)
   clearDictionaryListFromMenu() {
     for (var i = 0; i < this.mDictionaryItems.length; i++) {
       this.mDictionaryMenu.removeChild(this.mDictionaryItems[i]);
     }
     this.mDictionaryItems = [];
   },

--- a/toolkit/modules/tests/browser/browser_InlineSpellChecker.js
+++ b/toolkit/modules/tests/browser/browser_InlineSpellChecker.js
@@ -9,125 +9,16 @@ function test() {
 
   ok(InlineSpellChecker, "InlineSpellChecker class exists");
   for (var fname in tests) {
     tests[fname]();
   }
 }
 
 var tests = {
-  // Test various possible dictionary name to ensure they display as expected.
-  // XXX: This only works for the 'en-US' locale, as the testing involves localized output.
-  testDictionaryDisplayNames() {
-    let isc = new InlineSpellChecker();
-
-    // Check non-well-formed language tag.
-    is(isc.getDictionaryDisplayName("-invalid-"), "-invalid-", "'-invalid-' should display as '-invalid-'");
-
-    // XXX: It isn't clear how we'd ideally want to display variant subtags.
-
-    // Check valid language subtag.
-    is(isc.getDictionaryDisplayName("en"), "English", "'en' should display as 'English'");
-    is(isc.getDictionaryDisplayName("en-fonipa"), "English (fonipa)", "'en-fonipa' should display as 'English (fonipa)'");
-    is(isc.getDictionaryDisplayName("en-qxqaaaaz"), "English (qxqaaaaz)", "'en-qxqaaaaz' should display as 'English (qxqaaaaz)'");
-
-    // Check valid language subtag and valid region subtag.
-    is(isc.getDictionaryDisplayName("en-US"), "English (United States)", "'en-US' should display as 'English (United States)'");
-    is(isc.getDictionaryDisplayName("en-US-fonipa"), "English (United States) (fonipa)", "'en-US-fonipa' should display as 'English (United States) (fonipa)'");
-    is(isc.getDictionaryDisplayName("en-US-qxqaaaaz"), "English (United States) (qxqaaaaz)", "'en-US-qxqaaaaz' should display as 'English (United States) (qxqaaaaz)'");
-
-    // Check valid language subtag and invalid but well-formed region subtag.
-    is(isc.getDictionaryDisplayName("en-WO"), "English (WO)", "'en-WO' should display as 'English (WO)'");
-    is(isc.getDictionaryDisplayName("en-WO-fonipa"), "English (WO) (fonipa)", "'en-WO-fonipa' should display as 'English (WO) (fonipa)'");
-    is(isc.getDictionaryDisplayName("en-WO-qxqaaaaz"), "English (WO) (qxqaaaaz)", "'en-WO-qxqaaaaz' should display as 'English (WO) (qxqaaaaz)'");
-
-    // Check valid language subtag and valid script subtag.
-    todo_is(isc.getDictionaryDisplayName("en-Cyrl"), "English / Cyrillic", "'en-Cyrl' should display as 'English / Cyrillic'");
-    todo_is(isc.getDictionaryDisplayName("en-Cyrl-fonipa"), "English / Cyrillic (fonipa)", "'en-Cyrl-fonipa' should display as 'English / Cyrillic (fonipa)'");
-    todo_is(isc.getDictionaryDisplayName("en-Cyrl-qxqaaaaz"), "English / Cyrillic (qxqaaaaz)", "'en-Cyrl-qxqaaaaz' should display as 'English / Cyrillic (qxqaaaaz)'");
-    todo_is(isc.getDictionaryDisplayName("en-Cyrl-US"), "English (United States) / Cyrillic", "'en-Cyrl-US' should display as 'English (United States) / Cyrillic'");
-    todo_is(isc.getDictionaryDisplayName("en-Cyrl-US-fonipa"), "English (United States) / Cyrillic (fonipa)", "'en-Cyrl-US-fonipa' should display as 'English (United States) / Cyrillic (fonipa)'");
-    todo_is(isc.getDictionaryDisplayName("en-Cyrl-US-qxqaaaaz"), "English (United States) / Cyrillic (qxqaaaaz)", "'en-Cyrl-US-qxqaaaaz' should display as 'English (United States) / Cyrillic (qxqaaaaz)'");
-    todo_is(isc.getDictionaryDisplayName("en-Cyrl-WO"), "English (WO) / Cyrillic", "'en-Cyrl-WO' should display as 'English (WO) / Cyrillic'");
-    todo_is(isc.getDictionaryDisplayName("en-Cyrl-WO-fonipa"), "English (WO) / Cyrillic (fonipa)", "'en-Cyrl-WO-fonipa' should display as 'English (WO) / Cyrillic (fonipa)'");
-    todo_is(isc.getDictionaryDisplayName("en-Cyrl-WO-qxqaaaaz"), "English (WO) / Cyrillic (qxqaaaaz)", "'en-Cyrl-WO-qxqaaaaz' should display as 'English (WO) / Cyrillic (qxqaaaaz)'");
-
-    // Check valid language subtag and invalid but well-formed script subtag.
-    is(isc.getDictionaryDisplayName("en-Qaaz"), "English / Qaaz", "'en-Qaaz' should display as 'English / Qaaz'");
-    is(isc.getDictionaryDisplayName("en-Qaaz-fonipa"), "English / Qaaz (fonipa)", "'en-Qaaz-fonipa' should display as 'English / Qaaz (fonipa)'");
-    is(isc.getDictionaryDisplayName("en-Qaaz-qxqaaaaz"), "English / Qaaz (qxqaaaaz)", "'en-Qaaz-qxqaaaaz' should display as 'English / Qaaz (qxqaaaaz)'");
-    is(isc.getDictionaryDisplayName("en-Qaaz-US"), "English (United States) / Qaaz", "'en-Qaaz-US' should display as 'English (United States) / Qaaz'");
-    is(isc.getDictionaryDisplayName("en-Qaaz-US-fonipa"), "English (United States) / Qaaz (fonipa)", "'en-Qaaz-US-fonipa' should display as 'English (United States) / Qaaz (fonipa)'");
-    is(isc.getDictionaryDisplayName("en-Qaaz-US-qxqaaaaz"), "English (United States) / Qaaz (qxqaaaaz)", "'en-Qaaz-US-qxqaaaaz' should display as 'English (United States) / Qaaz (qxqaaaaz)'");
-    is(isc.getDictionaryDisplayName("en-Qaaz-WO"), "English (WO) / Qaaz", "'en-Qaaz-WO' should display as 'English (WO) / Qaaz'");
-    is(isc.getDictionaryDisplayName("en-Qaaz-WO-fonipa"), "English (WO) / Qaaz (fonipa)", "'en-Qaaz-WO-fonipa' should display as 'English (WO) / Qaaz (fonipa)'");
-    is(isc.getDictionaryDisplayName("en-Qaaz-WO-qxqaaaaz"), "English (WO) / Qaaz (qxqaaaaz)", "'en-Qaaz-WO-qxqaaaaz' should display as 'English (WO) / Qaaz (qxqaaaaz)'");
-
-    // Check invalid but well-formed language subtag.
-    is(isc.getDictionaryDisplayName("qaz"), "qaz", "'qaz' should display as 'qaz'");
-    is(isc.getDictionaryDisplayName("qaz-fonipa"), "qaz (fonipa)", "'qaz-fonipa' should display as 'qaz (fonipa)'");
-    is(isc.getDictionaryDisplayName("qaz-qxqaaaaz"), "qaz (qxqaaaaz)", "'qaz-qxqaaaaz' should display as 'qaz (qxqaaaaz)'");
-
-    // Check invalid but well-formed language subtag and valid region subtag.
-    is(isc.getDictionaryDisplayName("qaz-US"), "qaz (United States)", "'qaz-US' should display as 'qaz (United States)'");
-    is(isc.getDictionaryDisplayName("qaz-US-fonipa"), "qaz (United States) (fonipa)", "'qaz-US-fonipa' should display as 'qaz (United States) (fonipa)'");
-    is(isc.getDictionaryDisplayName("qaz-US-qxqaaaaz"), "qaz (United States) (qxqaaaaz)", "'qaz-US-qxqaaaaz' should display as 'qaz (United States) (qxqaaaaz)'");
-
-    // Check invalid but well-formed language subtag and invalid but well-formed region subtag.
-    is(isc.getDictionaryDisplayName("qaz-WO"), "qaz (WO)", "'qaz-WO' should display as 'qaz (WO)'");
-    is(isc.getDictionaryDisplayName("qaz-WO-fonipa"), "qaz (WO) (fonipa)", "'qaz-WO-fonipa' should display as 'qaz (WO) (fonipa)'");
-    is(isc.getDictionaryDisplayName("qaz-WO-qxqaaaaz"), "qaz (WO) (qxqaaaaz)", "'qaz-WO-qxqaaaaz' should display as 'qaz (WO) (qxqaaaaz)'");
-
-    // Check invalid but well-formed language subtag and valid script subtag.
-    todo_is(isc.getDictionaryDisplayName("qaz-Cyrl"), "qaz / Cyrillic", "'qaz-Cyrl' should display as 'qaz / Cyrillic'");
-    todo_is(isc.getDictionaryDisplayName("qaz-Cyrl-fonipa"), "qaz / Cyrillic (fonipa)", "'qaz-Cyrl-fonipa' should display as 'qaz / Cyrillic (fonipa)'");
-    todo_is(isc.getDictionaryDisplayName("qaz-Cyrl-qxqaaaaz"), "qaz / Cyrillic (qxqaaaaz)", "'qaz-Cyrl-qxqaaaaz' should display as 'qaz / Cyrillic (qxqaaaaz)'");
-    todo_is(isc.getDictionaryDisplayName("qaz-Cyrl-US"), "qaz (United States) / Cyrillic", "'qaz-Cyrl-US' should display as 'qaz (United States) / Cyrillic'");
-    todo_is(isc.getDictionaryDisplayName("qaz-Cyrl-US-fonipa"), "qaz (United States) / Cyrillic (fonipa)", "'qaz-Cyrl-US-fonipa' should display as 'qaz (United States) / Cyrillic (fonipa)'");
-    todo_is(isc.getDictionaryDisplayName("qaz-Cyrl-US-qxqaaaaz"), "qaz (United States) / Cyrillic (qxqaaaaz)", "'qaz-Cyrl-US-qxqaaaaz' should display as 'qaz (United States) / Cyrillic (qxqaaaaz)'");
-    todo_is(isc.getDictionaryDisplayName("qaz-Cyrl-WO"), "qaz (WO) / Cyrillic", "'qaz-Cyrl-WO' should display as 'qaz (WO) / Cyrillic'");
-    todo_is(isc.getDictionaryDisplayName("qaz-Cyrl-WO-fonipa"), "qaz (WO) / Cyrillic (fonipa)", "'qaz-Cyrl-WO-fonipa' should display as 'qaz (WO) / Cyrillic (fonipa)'");
-    todo_is(isc.getDictionaryDisplayName("qaz-Cyrl-WO-qxqaaaaz"), "qaz (WO) / Cyrillic (qxqaaaaz)", "'qaz-Cyrl-WO-qxqaaaaz' should display as 'qaz (WO) / Cyrillic (qxqaaaaz)'");
-
-    // Check invalid but well-formed language subtag and invalid but well-formed script subtag.
-    is(isc.getDictionaryDisplayName("qaz-Qaaz"), "qaz / Qaaz", "'qaz-Qaaz' should display as 'qaz / Qaaz'");
-    is(isc.getDictionaryDisplayName("qaz-Qaaz-fonipa"), "qaz / Qaaz (fonipa)", "'qaz-Qaaz-fonipa' should display as 'qaz / Qaaz (fonipa)'");
-    is(isc.getDictionaryDisplayName("qaz-Qaaz-qxqaaaaz"), "qaz / Qaaz (qxqaaaaz)", "'qaz-Qaaz-qxqaaaaz' should display as 'qaz / Qaaz (qxqaaaaz)'");
-    is(isc.getDictionaryDisplayName("qaz-Qaaz-US"), "qaz (United States) / Qaaz", "'qaz-Qaaz-US' should display as 'qaz (United States) / Qaaz'");
-    is(isc.getDictionaryDisplayName("qaz-Qaaz-US-fonipa"), "qaz (United States) / Qaaz (fonipa)", "'qaz-Qaaz-US-fonipa' should display as 'qaz (United States) / Qaaz (fonipa)'");
-    is(isc.getDictionaryDisplayName("qaz-Qaaz-US-qxqaaaaz"), "qaz (United States) / Qaaz (qxqaaaaz)", "'qaz-Qaaz-US-qxqaaaaz' should display as 'qaz (United States) / Qaaz (qxqaaaaz)'");
-    is(isc.getDictionaryDisplayName("qaz-Qaaz-WO"), "qaz (WO) / Qaaz", "'qaz-Qaaz-WO' should display as 'qaz (WO) / Qaaz'");
-    is(isc.getDictionaryDisplayName("qaz-Qaaz-WO-fonipa"), "qaz (WO) / Qaaz (fonipa)", "'qaz-Qaaz-WO-fonipa' should display as 'qaz (WO) / Qaaz (fonipa)'");
-    is(isc.getDictionaryDisplayName("qaz-Qaaz-WO-qxqaaaaz"), "qaz (WO) / Qaaz (qxqaaaaz)", "'qaz-Qaaz-WO-qxqaaaaz' should display as 'qaz (WO) / Qaaz (qxqaaaaz)'");
-
-    // Check multiple variant subtags.
-    todo_is(isc.getDictionaryDisplayName("en-Cyrl-US-fonipa-fonxsamp"), "English (United States) / Cyrillic (fonipa / fonxsamp)", "'en-Cyrl-US-fonipa-fonxsamp' should display as 'English (United States) / Cyrillic (fonipa / fonxsamp)'");
-    todo_is(isc.getDictionaryDisplayName("en-Cyrl-US-fonipa-qxqaaaaz"), "English (United States) / Cyrillic (fonipa / qxqaaaaz)", "'en-Cyrl-US-fonipa-qxqaaaaz' should display as 'English (United States) / Cyrillic (fonipa / qxqaaaaz)'");
-    todo_is(isc.getDictionaryDisplayName("en-Cyrl-US-fonipa-fonxsamp-qxqaaaaz"), "English (United States) / Cyrillic (fonipa / fonxsamp / qxqaaaaz)", "'en-Cyrl-US-fonipa-fonxsamp-qxqaaaaz' should display as 'English (United States) / Cyrillic (fonipa / fonxsamp / qxqaaaaz)'");
-    is(isc.getDictionaryDisplayName("qaz-Qaaz-WO-fonipa-fonxsamp"), "qaz (WO) / Qaaz (fonipa / fonxsamp)", "'qaz-Qaaz-WO-fonipa-fonxsamp' should display as 'qaz (WO) / Qaaz (fonipa / fonxsamp)'");
-    is(isc.getDictionaryDisplayName("qaz-Qaaz-WO-fonipa-qxqaaaaz"), "qaz (WO) / Qaaz (fonipa / qxqaaaaz)", "'qaz-Qaaz-WO-fonipa-qxqaaaaz' should display as 'qaz (WO) / Qaaz (fonipa / qxqaaaaz)'");
-    is(isc.getDictionaryDisplayName("qaz-Qaaz-WO-fonipa-fonxsamp-qxqaaaaz"), "qaz (WO) / Qaaz (fonipa / fonxsamp / qxqaaaaz)", "'qaz-Qaaz-WO-fonipa-fonxsamp-qxqaaaaz' should display as 'qaz (WO) / Qaaz (fonipa / fonxsamp / qxqaaaaz)'");
-
-    // Check numeric region subtag.
-    todo_is(isc.getDictionaryDisplayName("es-419"), "Spanish (Latin America and the Caribbean)", "'es-419' should display as 'Spanish (Latin America and the Caribbean)'");
-
-    // Check that extension subtags are ignored.
-    todo_is(isc.getDictionaryDisplayName("en-Cyrl-t-en-latn-m0-ungegn-2007"), "English / Cyrillic", "'en-Cyrl-t-en-latn-m0-ungegn-2007' should display as 'English / Cyrillic'");
-
-    // Check that privateuse subtags are ignored.
-    is(isc.getDictionaryDisplayName("en-x-ignore"), "English", "'en-x-ignore' should display as 'English'");
-    is(isc.getDictionaryDisplayName("en-x-ignore-this"), "English", "'en-x-ignore-this' should display as 'English'");
-    is(isc.getDictionaryDisplayName("en-x-ignore-this-subtag"), "English", "'en-x-ignore-this-subtag' should display as 'English'");
-
-    // Check that both extension and privateuse subtags are ignored.
-    todo_is(isc.getDictionaryDisplayName("en-Cyrl-t-en-latn-m0-ungegn-2007-x-ignore-this-subtag"), "English / Cyrillic", "'en-Cyrl-t-en-latn-m0-ungegn-2007-x-ignore-this-subtag' should display as 'English / Cyrillic'");
-
-    // XXX: Check grandfathered tags.
-  },
-
   testFlagsForInputs() {
     const HTML_NS = "http://www.w3.org/1999/xhtml";
     const {
       INPUT, EDITABLE, TEXTINPUT, NUMERIC, PASSWORD, SPELLCHECKABLE,
     } = SpellCheckHelper;
     const kExpectedResults = {
       "text": INPUT | EDITABLE | TEXTINPUT | SPELLCHECKABLE,
       "password": INPUT | EDITABLE | TEXTINPUT | PASSWORD,