title: Link existing Firebase and Google Cloud projects
body: <p>I am trying to migrate my Android app from GCM to FCM.<br>
  I use Google Cloud project for GCM and Firebase project for some Firebase features (Analytics, etc.) now. <br>
  <a href="https://developers.google.com/cloud-messaging/android/android-migrate-fcm" rel="nofollow noreferrer">Docs</a> say that I need to import Google Cloud project to Firebase, but I already have Firebase project for my app.
  As I understand, it is needed to provide GCM and FCM tokens compatibility.</p>
  
  <p>So, how to link existing Firebase and Google Cloud projects?<br>
  If it is impossible, is it possible to send messages to old tokens using new FCM endpoints and which credentials (Google Cloud or Firebase) should be used for it?</p>