image-picture-download-after-shrink.html

<!DOCTYPE html>
<script src="../resources/testharness.js"></script>
<script src="../resources/testharnessreport.js"></script>
<script>
    var t = async_test('Make sure that previously non-matching source based image resources are downloaded after the viewport changes.');
</script>
<iframe id=frame src="resources/image-picture-download-after-shrink-frame.html" width="700px"></iframe>
<script>
    window.addEventListener("message", t.step_func(function(msg) {
        if (msg.data == "shrink") {
            document.getElementsByTagName("iframe")[0].width = "150px";
        } else if (msg.data.indexOf("test_") != -1) {
            assert_equals(msg.data, "test_2");
            t.done();
        }
    }));

    // Since we want to see that a new resource wasn't downloaded, the only way is a timeout.
    setTimeout(t.step_func(function() {
        document.getElementById("frame").contentWindow.postMessage("test", "*");
    }), 500);
</script>

chromium/third_party/blink/web_tests/http/tests/loading/image-picture-download-after-shrink.html