I'm having problems using amp-bind within a PWA that uses the Shadow DOM.

Steps to reproduce:

1. Go to the example I've created at: https://www.edhollinghurst.com/amp-bind-pwa/amp-bind-pwa.html
2. Observe that if you click an answer it is correctly bound to the element used to display the answer.
3. Refresh the page. This should move you across to the 'PWA' with the 'App Shell' header displayed.
4. Trying clicking an answer. Observe that it is no longer bound to the element used to display the answer.

@choumx FYI