changed label into title

updated #1123

www/common/sframe-common-outer.js

@@ -73,7 +73,7 @@ define([
             ApiConfig.httpSafeOrigin + (pathname || window.location.pathname) + 'inner.html?' +
                 requireConfig.urlArgs + '#' + encodeURIComponent(JSON.stringify(req)));
         $i.attr('allowfullscreen', 'true');
-        $i.attr('aria-label', 'iframe'); // XXX
+        $i.attr('title', 'iframe');
         $('iframe-placeholder').after($i).remove();
 
         // This is a cheap trick to avoid loading sframe-channel in parallel with the