Issue 3697 - Fall back to i18n.getUILanguage if @ui_locale isn't supported

lib/utils.js

 /*
  * This file is part of Adblock Plus <https://adblockplus.org/>,
  * Copyright (C) 2006-2016 Eyeo GmbH
  *
  * Adblock Plus is free software: you can redistribute it and/or modify
  * it under the terms of the GNU General Public License version 3 as
  * published by the Free Software Foundation.
  *
  * Adblock Plus is distributed in the hope that it will be useful,
  * but WITHOUT ANY WARRANTY; without even the implied warranty of
@@ skipping 26 matching lines @@
       };
       document.addEventListener("DOMContentLoaded", onDOMContentLoaded);
     }
     else
     {
       setTimeout(callback, 0);
     }
   },
   get appLocale()
   {
-    var locale = ext.i18n.getMessage("@@ui_locale").replace(/_/g, "-");
+    var locale = ext.i18n.getMessage("@@ui_locale");
+    if (locale == "") {
+        locale = ext.i18n.getUILanguage();
+    }
+    locale = locale.replace(/_/g, "-");
     Object.defineProperty(this, "appLocale", {value: locale, enumerable: true});
     return this.appLocale;
   },
+  get readingDirection()
+  {
+    var direction = ext.i18n.getMessage("@@bidi_dir");
+    if (direction == "") {

[Sebastian Noack, 2016/05/12 22:14:29]

Nit: I would rather check for !direction, this reads a little easier and
automatically handles null and undefined along empty strings.

[Sebastian Noack, 2016/05/12 22:14:30]

Nit: Braces aren't required according to our coding practices in the case here.

+      direction = /^(ar|fa|he|ug|ur)(_|$)/.test(this.appLocale) ? "rtl" : "ltr";
+    }
+    Object.defineProperty(this, "readingDirection", {value: direction, enumerable: true});
+    return this.readingDirection;
+  },
   generateChecksum: function(lines)
   {
     // We cannot calculate MD5 checksums yet :-(
     return null;
   },
   makeURI: function(url)
   {
     return Services.io.newURI(url);
   },
 
@@ skipping 53 matching lines @@
   {
     var Prefs = require("prefs").Prefs;
     var docLink = Prefs.documentation_link;
     return docLink.replace(/%LINK%/g, linkID).replace(/%LANG%/g, Utils.appLocale);
   },
 
   yield: function()
   {
   }
 };