<!DOCTYPE html>
<script>
var width, url;
function maybeReport() {
  if (width !== undefined && url !== undefined) {
    window.parent.postMessage({status: "result",
                               width,
                               url}, "*");
  }
}
onload = function() {
  width = document.querySelector("img").width;
  maybeReport();
};
navigator.serviceWorker.onmessage = function(event) {
  url = event.data;
  maybeReport();
};
</script>
<img src="image-20px.png">
