FCM: Cannot click notification - firebase

Question

I'm using the recently release FCM messaging support for push notifications on the chrome. When my app is in the background, I get the notification but nothing happens when I click the notification. How to I specify the URL which should open when the user clicks the notification? (I understand how its done using the pure service worker concept using the notificationclick event, I want to know how to do that using FCM messaging.)
messaging.setBackgroundMessageHandler(function(payload) {
var data = payload || {};
var shinyData = decoder.run(data);
console.log('[firebase-messaging-sw.js] Received background message ', shinyData);
return self.registration.showNotification(shinyData.title, {
body: shinyData.body,
icon: shinyData.icon
})
});
What am I missing here?

Answer 1

click_action is not one of the possible parameters of the showNotification function.
To handle the click on the notification, define a notificationclick event handler.
For example:
self.addEventListener('notificationclick', function(event) {
event.notification.close();
event.waitUntil(self.clients.openWindow(YOUR_URL_HERE));
});

Answer 2

Marco's answer is correct.
The Firebase Messaging Library is a wrapper on top of the Web Push API.
The notification: { click_action: 'https://...' } payload will show a notification and handle the click for you. To achieve the same with data payload you should implement the notificationclick event listener (Like Marco suggested).
self.addEventListener('notificationclick', function(event) {
event.notification.close();
... Do your stuff here.
});
You can also do the same with the notificationclose event:
self.addEventListener('notificationclose', function(event) {
... Do your stuff here.
});