LayoutTests/http/tests/images/webp-progressive-load.html

<img style="background-color: red" >
<script>
if (window.testRunner) {
    testRunner.dumpAsText(pixelTest = true);
    testRunner.waitUntilDone();
}

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

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

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

function runTest()
{
    var image = document.getElementsByTagName('img')[0];
    image.src = loadAndStall() + webpImage() + "&stallAt=4237&stallFor=1";
    setTimeout(testDone, 3000);
}

setTimeout(runTest, 1);
</script>