mall_img_src;
      beforeLoad = performance.now();
    }, 0);
    new PerformanceObserver(
      t.step_func(entryList => {
        let images = entryList.getEntries().filter(e => e.id !== '');
        if (!images.length)
          return;
        assert_equals(images.length, 1, 'Should only receive one entry');
        const entry = images[0];
        checkImage(images[0], window.location.origin + small_img_src, 'target2', 16 * 16,
            beforeLoad);
        t.done();
      })
    ).observe({type: '