title: GCM to FCM Migration: client subscription question
body: <p>For a new Firebase project I add the SenderId to my desktop websites manifest (and do not use VAPID authentication). </p>
  
  <p>On a successful pushManager.subscription() the token I get back from the pushSubscription is of the format:</p>
  
  <pre><code>https://android.googleapis.com/gcm/send/*instance_token*
  </code></pre>
  
  <p>I expected it to be using the firebase endpoint instead:</p>
  
  <pre><code>https://fcm.googleapis.com/fcm/send/*instance_token*
  </code></pre>
  
  <p>I can successfully send push notifications to this token through the firebase endpoint.</p>
  
  <p>My questions are:</p>
  
  <ol>
  <li><p>Why do I get a GCM endpoint in the token for a firebase project? </p></li>
  <li><p>Will this always be the case or is something going to change when GCM is discontinued? </p></li>
  <li><p>Can we continue to use the legacy approach of the gcm_sender_id in the manifest (over VAPID)?</p></li>
  </ol>