<!DOCTYPE html>
<iframe id=frame srcdoc="
<script>
const style = document.createElement('style');
style.textContent = '@import url(data:text/css,)';
document.head.appendChild(style);
style.remove();
</script>">
</iframe>
This test passes if it doesn't assert.
<script>
if (window.testRunner) {
    testRunner.dumpAsText();
    testRunner.waitUntilDone();
}
    
function end() {
    if (window.GCController)
        GCController.collect();
    testRunner.notifyDone();
}

frame.onload = () => {
    frame.remove();
    setTimeout(end, 0);
};
</script>