Ionic 2 Google FCM push notification icon

Im having some kind of trouble setting my Ionic's icon when I send a push notification through FCM. My notification looks like:

var mensaje = {
  "notification":{
    "title": "Some title",
    "body":"Body",
    "sound":"default",
    "click_action":"FCM_PLUGIN_ACTIVITY",
    "icon": "?????"
  },
  "data":{
    "title": "Title",
    "url": "url"
  }
};

In the ionic app into resources folder I have an logo.png that's the one that I want to use for the notification. What route or string should I send to this image to be shown?

via San Pupi