--- a/calendar/base/modules/calCalendarDeactivator.jsm
+++ b/calendar/base/modules/calCalendarDeactivator.jsm
@@ -1,21 +1,18 @@
 /* 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/. */
 
 this.EXPORTED_SYMBOLS = ["calendarDeactivator"];
 
 const { Services } = ChromeUtils.import("resource://gre/modules/Services.jsm");
 const { cal } = ChromeUtils.import("resource:///modules/calendar/calUtils.jsm");
-const { Localization } = ChromeUtils.import("resource://gre/modules/Localization.jsm");
 
-const syncL10n = new Localization(["calendar/calendar-widgets.ftl"], true);
-syncL10n.setIsSync(true);
-syncL10n.init();
+var l10n = new Localization(["calendar/calendar-widgets.ftl"], true);
 
 /**
  * Handles deactivation of calendar UI and background processes/services (such
  * as the alarms service) when users do not want to use calendar functionality.
  * Also handles re-activation when users change their mind.
  *
  * If all of a user's calendars are disabled (e.g. calendar > properties >
  * "turn this calendar on") then full calendar functionality is deactivated.
@@ -124,17 +121,17 @@ var calendarDeactivator = {
     ];
 
     for (let [notificationbox, messageName] of notificationboxes) {
       let existingNotification = notificationbox.getNotificationWithValue(value);
 
       if (calendarIsActivated) {
         notificationbox.removeNotification(existingNotification);
       } else if (!existingNotification) {
-        let message = syncL10n.formatValueSync(messageName);
+        let message = l10n.formatValueSync(messageName);
         let priority = notificationbox.PRIORITY_WARNING_MEDIUM;
 
         notificationbox.appendNotification(message, value, null, priority, null);
       }
     }
   },
 
   // calICalendarManagerObserver methods

--- a/chat/content/otr-finger.js
+++ b/chat/content/otr-finger.js
@@ -1,21 +1,16 @@
 /* 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 { Services } = ChromeUtils.import("resource:///modules/imServices.jsm");
 var { OTR } = ChromeUtils.import("resource:///modules/OTR.jsm");
-var { Localization } = ChromeUtils.import(
-  "resource://gre/modules/Localization.jsm"
-);
 
-var l10n = new Localization(["messenger/otr/finger-sync.ftl"]);
-l10n.setIsSync(true);
-l10n.init();
+var l10n = new Localization(["messenger/otr/finger-sync.ftl"], true);
 
 var gFingers;
 var fingerTreeView = {
   selection: null,
   rowCount: 0,
 
   setTree(tree) {},
   getImageSrc(row, column) {},

--- a/chat/modules/OTR.jsm
+++ b/chat/modules/OTR.jsm
@@ -1,36 +1,30 @@
 /* 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/. */
 
-const { Localization } = ChromeUtils.import(
-  "resource://gre/modules/Localization.jsm"
-);
 const { BasePromiseWorker } = ChromeUtils.import(
   "resource://gre/modules/PromiseWorker.jsm"
 );
 const { OS } = ChromeUtils.import("resource://gre/modules/osfile.jsm");
 const { ctypes } = ChromeUtils.import("resource://gre/modules/ctypes.jsm");
 const { Services } = ChromeUtils.import("resource:///modules/imServices.jsm");
 const { CLib } = ChromeUtils.import("resource:///modules/CLib.jsm");
 const { OTRLibLoader } = ChromeUtils.import("resource:///modules/OTRLib.jsm");
-var workerPath = "chrome://chat/content/otrWorker.js";
 const { OTRHelpers } = ChromeUtils.import("resource:///modules/OTRHelpers.jsm");
 
-const syncL10n = new Localization(["messenger/otr/otr.ftl"]);
-syncL10n.setIsSync(true);
-syncL10n.init();
+var l10n = new Localization(["messenger/otr/otr.ftl"], true);
 
 function _str(id) {
-  return syncL10n.formatValueSync(id);
+  return l10n.formatValueSync(id);
 }
 
 function _strArgs(id, args) {
-  return syncL10n.formatValueSync(id, args);
+  return l10n.formatValueSync(id, args);
 }
 
 // some helpers
 
 function setInterval(fn, delay) {
   let timer = Cc["@mozilla.org/timer;1"].createInstance(Ci.nsITimer);
   timer.init(fn, delay, Ci.nsITimer.TYPE_REPEATING_SLACK);
   return timer;
@@ -232,17 +226,17 @@ var OTR = {
 
     if (!address) {
       OTRLib.otrl_privkey_generate_cancelled(OTR.userstate, newkey);
       throw new Error(
         "generatePrivateKey failed to parse ptr.toSource(): " + keyPtrSrc
       );
     }
 
-    let worker = new BasePromiseWorker(workerPath);
+    let worker = new BasePromiseWorker("chrome://chat/content/otrWorker.js");
     return worker
       .post("generateKey", [OTRLib.path, OTRLib.otrl_version, address])
       .then(function() {
         let err = OTRLib.otrl_privkey_generate_finish(
           OTR.userstate,
           newkey,
           OTR.privateKeyPath
         );

--- a/chat/modules/OTRUI.jsm
+++ b/chat/modules/OTRUI.jsm
@@ -1,30 +1,25 @@
 /* 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/. */
 
 this.EXPORTED_SYMBOLS = ["OTRUI"];
 
-const { Localization } = ChromeUtils.import(
-  "resource://gre/modules/Localization.jsm"
-);
 const { Services } = ChromeUtils.import("resource:///modules/imServices.jsm");
 const { OTR } = ChromeUtils.import("resource:///modules/OTR.jsm");
 
-const syncL10n = new Localization(["messenger/otr/otrUI.ftl"]);
-syncL10n.setIsSync(true);
-syncL10n.init();
+var l10n = new Localization(["messenger/otr/otrUI.ftl"], true);
 
 function _str(id) {
-  return syncL10n.formatValueSync(id);
+  return l10n.formatValueSync(id);
 }
 
 function _strArgs(id, args) {
-  return syncL10n.formatValueSync(id, args);
+  return l10n.formatValueSync(id, args);
 }
 
 const OTR_AUTH_DIALOG_URL = "chrome://chat/content/otr-auth.xhtml";
 const OTR_ADD_FINGER_DIALOG_URL =
   "chrome://chat/content/otr-add-fingerprint.xhtml";
 
 const AUTH_STATUS_UNVERIFIED = "otr-auth-unverified";
 var authLabelMap;
@@ -422,19 +417,19 @@ var OTRUI = {
         OTRUI.noOtrPossible(otrContainer, context);
         return;
       }
       if (addSystemMessage) {
         let trust = OTRUI.getTrustSettings(context);
         let id = "state-" + trust.class;
         let msg;
         if (OTR.trust(context) == OTR.trustState.TRUST_NOT_PRIVATE) {
-          msg = syncL10n.formatValueSync(id);
+          msg = l10n.formatValueSync(id);
         } else {
-          msg = syncL10n.formatValueSync(id, { name: context.username });
+          msg = l10n.formatValueSync(id, { name: context.username });
         }
         uiConv.systemMessage(msg);
       }
     } catch (e) {
       OTRUI.noOtrPossible(otrContainer, context);
       return;
     }
 
@@ -594,17 +589,17 @@ var OTRUI = {
       msg,
       context.username,
       null,
       priority,
       buttons,
       null
     );
 
-    let verifyTitle = syncL10n.formatValueSync("verify-title");
+    let verifyTitle = l10n.formatValueSync("verify-title");
     this.updateNotificationUI(
       context,
       verifyTitle,
       context.username,
       AUTH_STATUS_UNVERIFIED
     );
 
     if (!this.visibleConv) {

--- a/mail/base/content/mailWidgets.js
+++ b/mail/base/content/mailWidgets.js
@@ -29,24 +29,20 @@
   const { DBViewWrapper } = ChromeUtils.import(
     "resource:///modules/DBViewWrapper.jsm"
   );
   const { TagUtils } = ChromeUtils.import("resource:///modules/TagUtils.jsm");
   var { MimeParser } = ChromeUtils.import("resource:///modules/mimeParser.jsm");
   var { DisplayNameUtils } = ChromeUtils.import(
     "resource:///modules/DisplayNameUtils.jsm"
   );
-  var { Localization } = ChromeUtils.import(
-    "resource://gre/modules/Localization.jsm"
+  var l10n = new Localization(
+    ["messenger/messengercompose/messengercompose.ftl"],
+    true
   );
-  var l10n = new Localization([
-    "messenger/messengercompose/messengercompose.ftl",
-  ]);
-  l10n.setIsSync(true);
-  l10n.init();
 
   class MozMailHeaderfield extends MozXULElement {
     connectedCallback() {
       this.setAttribute("context", "copyPopup");
       this.classList.add("headerValue");
     }
 
     set headerValue(val) {

--- a/mail/base/content/specialTabs.js
+++ b/mail/base/content/specialTabs.js
@@ -16,19 +16,16 @@ var { AddonManager } = ChromeUtils.impor
   "resource://gre/modules/AddonManager.jsm"
 );
 var { StringBundle } = ChromeUtils.import(
   "resource:///modules/StringBundle.jsm"
 );
 var { ExtensionParent } = ChromeUtils.import(
   "resource://gre/modules/ExtensionParent.jsm"
 );
-var { Localization } = ChromeUtils.import(
-  "resource://gre/modules/Localization.jsm"
-);
 
 function tabProgressListener(aTab, aStartsBlank) {
   this.mTab = aTab;
   this.mBrowser = aTab.browser;
   this.mBlank = aStartsBlank;
   this.mProgressListener = null;
 }
 
@@ -379,19 +376,17 @@ var contentTabBaseType = {
 
     // Let's not mess with about:blank.
     null,
 
     // about:profiles
     function(aDocument, aTab) {
       // Need a timeout to let the script run to create the needed buttons.
       setTimeout(() => {
-        let l10n = new Localization(["messenger/aboutProfilesExtra.ftl"]);
-        l10n.setIsSync(true);
-        l10n.init();
+        let l10n = new Localization(["messenger/aboutProfilesExtra.ftl"], true);
         for (let button of aDocument.querySelectorAll(
           `[data-l10n-id="profiles-launch-profile"]`
         )) {
           button.textContent = l10n.formatValueSync(
             "profiles-launch-profile-plain"
           );
         }
       }, 500);

--- a/mail/components/compose/content/MsgComposeCommands.js
+++ b/mail/components/compose/content/MsgComposeCommands.js
@@ -48,24 +48,20 @@ var { PluralForm } = ChromeUtils.import(
 var { Services } = ChromeUtils.import("resource://gre/modules/Services.jsm");
 var { AppConstants } = ChromeUtils.import(
   "resource://gre/modules/AppConstants.jsm"
 );
 var { MailConstants } = ChromeUtils.import(
   "resource:///modules/MailConstants.jsm"
 );
 
-var { Localization } = ChromeUtils.import(
-  "resource://gre/modules/Localization.jsm"
+var l10n = new Localization(
+  ["messenger/messengercompose/messengercompose.ftl"],
+  true
 );
-var l10n = new Localization([
-  "messenger/messengercompose/messengercompose.ftl",
-]);
-l10n.setIsSync(true);
-l10n.init();
 
 ChromeUtils.defineModuleGetter(this, "OS", "resource://gre/modules/osfile.jsm");
 ChromeUtils.defineModuleGetter(
   this,
   "ShortcutUtils",
   "resource://gre/modules/ShortcutUtils.jsm"
 );
 

--- a/mail/components/preferences/general.js
+++ b/mail/components/preferences/general.js
@@ -25,19 +25,16 @@ var { XPCOMUtils } = ChromeUtils.import(
   "resource://gre/modules/XPCOMUtils.jsm"
 );
 var { AppConstants } = ChromeUtils.import(
   "resource://gre/modules/AppConstants.jsm"
 );
 var { L10nRegistry } = ChromeUtils.import(
   "resource://gre/modules/L10nRegistry.jsm"
 );
-var { Localization } = ChromeUtils.import(
-  "resource://gre/modules/Localization.jsm"
-);
 var { Services } = ChromeUtils.import("resource://gre/modules/Services.jsm");
 var { UpdateUtils } = ChromeUtils.import(
   "resource://gre/modules/UpdateUtils.jsm"
 );
 var { TagUtils } = ChromeUtils.import("resource:///modules/TagUtils.jsm");
 
 XPCOMUtils.defineLazyServiceGetters(this, {
   gHandlerService: [

--- a/mailnews/base/content/msgAccountCentral.js
+++ b/mailnews/base/content/msgAccountCentral.js
@@ -5,19 +5,17 @@
 
 /* import-globals-from ../../../mail/base/content/mailCore.js */
 /* import-globals-from ../prefs/content/accountUtils.js */
 
 var { Services } = ChromeUtils.import("resource://gre/modules/Services.jsm");
 var { MailServices } = ChromeUtils.import(
   "resource:///modules/MailServices.jsm"
 );
-var l10n = new Localization(["messenger/accountCentral.ftl"]);
-l10n.setIsSync(true);
-l10n.init();
+var l10n = new Localization(["messenger/accountCentral.ftl"], true);
 
 var gSelectedServer = null;
 var gSelectedFolder = null;
 
 /**
  * Set up the whole page depending on the selected folder/account.
  * The folder is passed in via the document URL.
  */