title: Open app on firebase notification received (FCM)
body: <p>I want to open application automatically when notification is received, is this possible with Firebase and new FCM notifications?</p>
  
  <p>I know I can set click_action but that's only for customizing which activity will start on notification click, I need something that will start automatically when notification is received.</p>
  
  <p>I tried the quick start messaging firebase sample and there is a onMessageReceived() method but it only works if the app is in foreground. Is there something that will execute while app is in background as well?
  GCM could do something like what I want here by directly starting activity intent from broadcast receiver which is called when notification is received.</p>