ulPaint, "LargestContentfulPaint is not implemented");
      let beforeLoad = performance.now();
      let beforeSecondImageLoad = performance.now();
      let firstCallback = true;
      // black-rectangle.png is 50 x 25.
      const original_rect_size = 50 * 25;
      // The bigger black rectangle is 100 x 50, but defined with width="50".
      const bigger_rect_size = 100 * 50;
      const observer = new PerformanceObserver(
        t.step_func(function (entryList) {
          assert_equals(entryList.get