LayoutTests/fast/canvas/offscreen-enabled.html

<script>
    function log(msg) {
        const out = document.querySelector("div");
        const p = document.createElement("p");
        p.textContent = msg;
        out.appendChild(p);
    }
    if (window.testRunner)
        window.testRunner.dumpAsText();

    window.addEventListener("load", function () {
        log('createImageBitmap' in window ? "createImageBitmap exists" : "FAIL: createImageBitmap should exist");
        log('OffscreenCanvas' in window ? "OffscreenCanvas exists" : "FAIL: OffscreenCanvas should exist");
    }, false);
</script>
<div></div>