push notifications seem to work in FF and Chrome

service-worker.js

@@ -0,0 +1,23 @@
+// Must be located at the root.
+'use strict';
+
+importScripts("https://unpkg.com/firebase@5.5.0/firebase-app.js");
+importScripts("https://unpkg.com/firebase@5.5.0/firebase-messaging.js");
+
+const FIREBASE_PUBLIC_API_KEY = "AIzaSyD6X4ULR-RUsobvs1zZ2bHdJuPz39q2tbQ";
+const FIREBASE_SENDER_ID = "114126160546";
+
+firebase.initializeApp({
+  apiKey: FIREBASE_PUBLIC_API_KEY,
+  messagingSenderId: FIREBASE_SENDER_ID
+});
+
+firebase.messaging().setBackgroundMessageHandler(function(payload) {
+  let title = payload.notification.title || "New message";
+  let options = {
+    body: payload.notification.body || "",
+    icon: '/img/logo96.png'
+  };
+
+  return self.registration.showNotification(title, options);
+});