This is a test for <a href="https://bugs.webkit.org/show_bug.cgi?id=19541">https://bugs.webkit.org/show_bug.cgi?id=19541</a> 
RBug 19541: Null pointer in showModalDialog()

This tests calling the showModalDialog() function on a window object from a detached iframe, both calling the saved showModalDialog() function and getting the property again after the iframe has been detached.

If there is no crash this test passes.
<script type="text/javascript">
if (window.testRunner)
    testRunner.dumpAsText();

var iframe = document.createElement("iframe");

iframe.onload = function() {
    var iframeWindow = iframe.contentWindow;
    var f = iframeWindow.showModalDialog;

    iframe.parentNode.removeChild(iframe);
    if (iframeWindow.showModalDialog)
        iframeWindow.showModalDialog();
    if (f)
        f.call(iframeWindow);
};

document.body.appendChild(iframe);
</script>