FF webext does not support getBytesInUse()

src/js/settings.js

@@ -109,7 +109,11 @@ var exportToFile = function() {
 
 var onLocalDataReceived = function(details) {
     uDom('#localData > ul > li:nth-of-type(1)').text(
-        vAPI.i18n('settingsStorageUsed').replace('{{value}}', details.storageUsed.toLocaleString())
+        vAPI.i18n('settingsStorageUsed')
+            .replace(
+                '{{value}}',
+                typeof details.storageUsed === 'number' ? details.storageUsed.toLocaleString() : '?'
+            )
     );
 
     var elem, dt;

src/js/storage.js

@@ -1,7 +1,7 @@
 /*******************************************************************************
 
-    uBlock - a browser extension to block requests.
-    Copyright (C) 2014-2015 Raymond Hill
+    uBlock Origin - a browser extension to block requests.
+    Copyright (C) 2014-2016 Raymond Hill
 
     This program is free software: you can redistribute it and/or modify
     it under the terms of the GNU General Public License as published by
@@ -19,7 +19,7 @@
     Home: https://github.com/gorhill/uBlock
 */
 
-/* global YaMD5, µBlock, vAPI, punycode, publicSuffixList */
+/* global YaMD5, punycode, publicSuffixList */
 
 'use strict';
 
@@ -33,7 +33,12 @@
         µBlock.storageUsed = bytesInUse;
         callback(bytesInUse);
     };
+    // Not all platforms implement this method.
+    if ( vAPI.storage.getBytesInUse instanceof Function ) {
         vAPI.storage.getBytesInUse(null, getBytesInUseHandler);
+    } else {
+        callback();
+    }
 };
 
 /******************************************************************************/