<script>
if (window.testRunner)
    testRunner.dumpAsText();

function runTest() {
    var text = document.getElementById('iframe').contentDocument.documentElement.outerText;
    result.innerHTML = text;
}
</script>
<setvar id="result">
<script>
document.write('<iframe id="iframe" src="data:text/plain,FAIL" onload="runTest()">')
var oRTE = frames[0].document; 
oRTE.write("PASS");
oRTE.close();
</script>