splay" helper-iframe-url="<%host%>/webpush/amp-web-push-helper-frame.html" permission-dialog-url="<%host%>/webpush/amp-web-push-permission-dialog.html" service-worker-url="<%host%>/sw.js">
    </amp-web-push>

    <!-- Clicking the subscription widget pops up a page prompting the user for notification permissions and signals the service worker (configured below) to subscribe the user to push in the background. On this example, we are intercepting the call to `onMessageReceivedSubscribe`, and storing the sub