In its current implementation (as of June 2016) the native infowindow does not support event handlers, so interactive infowindows are out. For example:
<google-map-marker ...>
<paper-button on-tap="makeReservation">Reserve</paper-button>
...
</google-map-marker>
This will not work because the on-tap binding is lost when the infowindow is built. There is an issue open #288, but as of now it is not resolved.
If you don't need event handlers in the infowindow use the native infowindow. If you do, this element may help you.
The paper-map-info control emulates the functions of the native infowindow, but in a way that allows most any content to be composed inside. You can have interactive controls like buttons or iron-pages that depend on event bindings.