wrap firebase auth with test waiters

[gabrielgrant]

fixes #312

I've added the wrapper to the OAuth popup login path too, though it's not totally clear how this interacts with an ember acceptance test: running the tests in the browser seems seems to work with facebook login (so long as I've already authenticated the browser with the app manually) but I haven't thoroughly tested with other OAuth providers

[tstirrat]

Thanks for this, I like the idea, but think we can remove a lot of the duplication.

I wonder if we can clean this up by adding a node style to promise wrapper that also inserts the test waiters:

var authCalls = 0;

// ...
promisify: function(ref, methodName, args) {
  return new Ember.RSVP.Promise((resolve, reject) => {
    if (Ember.testing) {
      Ember.Test.registerWaiter(() => authCalls === 0); 
    }
    authCalls++;
    var callback = function(error, authData) {
      authCalls--;
      if (error) { 
        reject(error);
      } else {
        resolve(authData);
      }
    };

    args.push(callback);
    ref[methodName].apply(args)
  });
}

// called like so
return this.promisify(this.get('firebase'), 'authWithCustomToken', [options.token]);

[gabrielgrant]

Hey, @tstirrat sorry for the delay in getting back to this. While my quick hack got this working for me, you're right that a promise wrapper is probably a cleaner way to go to avoid the duplication.

[tstirrat]

I'm currently in the process of adding waiters to all the model requests. So I can cover this auth stuff in that PR, too.

More than happy for you to fix up this PR in the meantime, just let me know, either way.

[tstirrat]

Closing this in favor of #344 where I will use a common mixin