title: Google Sign in failing due to SharedElementCallback
body: <p>I have used pretty much the boilerplate from firebase and google sign on documentation. I get the dialog for choosing the account to log in from, and then it fails. I have updated my google play services. And also regenerated my sha1 keys. One thing that I have noticed is that android studio keeps giving me back the old key when executing the signingreport task, tho I have generated keys twice after that, and also updated on the firebase console.</p>
  
  <p><a href="https://gist.github.com/opheliagame/495375568db9f468139a594ac923807a" rel="nofollow noreferrer">Gist of the main activity on github</a></p>
  
  <pre><code>E/dalvikvm: Could not find class 'android.support.v4.app.ActivityCompat$SharedElementCallback23Impl', referenced from method android.support.v4.app.ActivityCompat.setEnterSharedElementCallback
  E/dalvikvm: Could not find class 'android.support.v4.app.ActivityCompat$SharedElementCallback21Impl', referenced from method android.support.v4.app.ActivityCompat.setEnterSharedElementCallback
  E/dalvikvm: Could not find class 'android.support.v4.app.ActivityCompat$SharedElementCallback23Impl', referenced from method android.support.v4.app.ActivityCompat.setExitSharedElementCallback
  E/dalvikvm: Could not find class 'android.support.v4.app.ActivityCompat$SharedElementCallback21Impl', referenced from method android.support.v4.app.ActivityCompat.setExitSharedElementCallback
  </code></pre>