Carve out an exception for embedded credentials in XHR.

third_party/WebKit/LayoutTests/http/tests/xmlhttprequest/null-auth.php

 <p>Test that null values in XHR login/password parameters are treated correctly.</p>
 <p>No auth tokens should be sent with this request.</p>
 <pre id='syncResult'> </pre>
 <script>
 if (window.testRunner)
   testRunner.dumpAsText();
 
-try {
-  req = new XMLHttpRequest;
-  req.open('POST', '<?php echo 'http://foo:bar@' . $_SERVER['HTTP_HOST'] . '/xmlhttprequest/resources/echo-auth.php' ?>', false, null, null);
-  req.send();
-  console.log("Fail: credentialed URLs should throw.");
-} catch (e) {
-  console.log("Pass: credentialed URL threw.");
-}
+req = new XMLHttpRequest;
+req.open('POST', '<?php echo 'http://foo:bar@' . $_SERVER['HTTP_HOST'] . '/xmlhttprequest/resources/echo-auth.php' ?>', false, null, null);
+req.send();
+document.getElementById('syncResult').firstChild.nodeValue = req.responseText;
 </script>