Bug 1106119 - fix locale detection for menu panel, r=mconley

--HG--
extra : rebase_source : c8a195a8bcccfb514dde04f5537ba29d9c36b493

browser/components/customizableui/content/panelUI.js

@@ -515,19 +515,11 @@ const PanelUI = {
  * @return  the selected locale or "en-US" if none is selected
  */
 function getLocale() {
-  const PREF_SELECTED_LOCALE = "general.useragent.locale";
   try {
-    let locale = Services.prefs.getComplexValue(PREF_SELECTED_LOCALE,
-                                                Ci.nsIPrefLocalizedString);
-    if (locale)
-      return locale;
-  }
-  catch (e) { }
-
-  try {
-    return Services.prefs.getCharPref(PREF_SELECTED_LOCALE);
-  }
-  catch (e) { }
-
+    let chromeRegistry = Cc["@mozilla.org/chrome/chrome-registry;1"]
+                           .getService(Ci.nsIXULChromeRegistry);
+    return chromeRegistry.getSelectedLocale("browser");
+  } catch (ex) {
     return "en-US";
+  }
 }