title: Using both Google Signin and Firebase auth require login twice?
body: <p>I ran into an probably, to some users, confusing issue:</p>
  
  <p>I'm using in my application <code>Firebase</code> to store the users data etc. and to have the user's data protected I use the build in <code>Google Authentication</code>. I recognized that I can define <code>scopes</code> at this signIn process, which the user can/should allow, but I although noticed that you can't ask for ALL of the Google Scopes/Services, (all with <code>Firebase</code> built in functionality)</p>
  
  <p>so I have to use the <code>Google JS Library</code> as well for authentication, to access the rest of the User data (I want to show the user in my Web-App) stored on <code>Google</code>.</p>
  
  <p>And maybe it could be kind of confusing if the <code>Google signin popup</code> shows <strong>twice</strong>, one auth to <code>Firebase</code> and another auth to <code>Google API's</code>.</p>
  
  <p>My question is, Is there a way to, maybe hand over the <code>access_token</code> at the <code>Firebase signin process</code> (or vice versa), that I don't have the user signin <strong>twice</strong> and the <code>Google popup</code> shows up only <strong>once</strong>?</p>