Two facebook logins in two instances of the app

I am developing a multiplayer app with facebook login (facebook sdk) and unity 4.6 beta and use the new UI. I can quickly test one user session from within the editor , the problem is that I want to quickly iterate the multiplayer testing with two fb users connected at the same time (one from unity editor and another one in web player or something very fast which doesn't require uploading the app somewhere).

I have set up in facebook developer portal app settings that it is a website app with domain "localhost" and gave it the localhost url. If I export the project for web player nothing happens and I get this in the unity webplayer log :

 Type IPointerClickHandler expected Button received. i:0. Facebook object is not yet loaded.  Did you call FB.Init()?

Did anyone encounter problems with this and found a solution for running 2 unity instances with 2 fb users on the same machine?