Move wrapSync from a class method to the instance.

@@ -265,14 +265,15 @@ define(function(require) {
             };
             bindMethods(this, 'login', 'logout');
         },
-    }, {
-        FacebookProvider: FacebookProvider,
-        FormProvider: FormProvider,
-        wrapSync: function(auth, origSync) {
+        wrapSync: function(origSync) {
+            var auth = this;
             return function() {
                 return authSync.apply(this, [auth, origSync].concat(_.toArray(arguments)));
             };
         },
+    }, {
+        FacebookProvider: FacebookProvider,
+        FormProvider: FormProvider,
     });
     return Auth;
 });