_func_done(function(entryList) {
        assert_equals(entryList.getEntries().length, 1);
        const entry = entryList.getEntries()[0];

        const url = window.location.origin + '/images/blue.png';
        // blue.png is 133 by 106.
        const size = 133 * 106;
        checkImage(entry, url, 'image_id', size, beforeLoad);
      })
    );
    observer.observe({type: 'largest-contentful-paint', buffered: true});
  }, 'Same-origin image after a JS initiated scroll event is observable.');
  document.b