Getting the Initial Ostate From Fire Base

The way you get the initial ostate from fire base is by using this import called on ostate changed. It sets up a listener for the ostate change, they call an observer. And it gives you a call back that runs every time it changes. Ho could have two browser windows open and one would get this call back fired. You could be logged in, close the browser, reopen it, and then this callback will fire as soon as it verifies the session is still authentic.