chromium/src/third_party/blink/web_tests/http/tests/images/webp-partial-load.html

<img style="background-color: blue" >
<script>
if (window.testRunner)
    testRunner.waitUntilDone();

function loadAndStall()
{
    return "http://127.0.0.1:8000/resources/load-and-stall.php";
}

function webpImage()
{
    return "?name=../../../images/resources/test.webp&mimeType=image%2Fwebp";
}

function testDone()
{
    if (window.testRunner) testRunner.notifyDone();
}

function runTest()
{
    var image = document.getElementsByTagName('img')[0];
    image.src = loadAndStall() + webpImage() + "&stallAt=2400&stallFor=60";
    setTimeout(testDone, 1500);
}

window.onload = function() {
    setTimeout(runTest, 0);
}
</script>