Entries().length, 1);
          const entry = entryList.getEntries()[0];
          const url = window.location.origin + '/images/black-rectangle.png';
          if (firstCallback) {
            // Checks the original black rectangle.
            // TODO(https://crbug.com/1411616): we're testing approximated values.
            checkImage(entry, url, 'image_id', original_rect_size,
              beforeLoad, ["approximateSize"]);
            // Creates a new bigger black rectangle.
            const img = doc