Add cross-origin test with credentials.

pkg/unittest/lib/html_config.dart

Index: pkg/unittest/lib/html_config.dart
diff --git a/pkg/unittest/lib/html_config.dart b/pkg/unittest/lib/html_config.dart
index 3d87f98a77b9ea89c1cb406646c93778d2ad583d..b0225e0376a73799e4884168800e305e606771f9 100644
--- a/pkg/unittest/lib/html_config.dart
+++ b/pkg/unittest/lib/html_config.dart
@@ -143,6 +143,19 @@ class HtmlConfiguration extends Configuration {
   }
 }
 
+/**
+ * Examine the url for this test to determine what the cross-origin port is for
+ * this test.
+ */
+int getCrossOriginPortNumber() {
+  var searchUrl = window.location.search;
+  var crossOriginStr = 'crossOriginPort=';
+  var index = searchUrl.indexOf(crossOriginStr);
+  var nextArg = searchUrl.indexOf('&', index);
+  return int.parse(searchUrl.substring(index + crossOriginStr.length,
+      nextArg == -1 ? searchUrl.length : nextArg));
+}
+
 void useHtmlConfiguration([bool isLayoutTest = false]) {
   configure(new HtmlConfiguration(isLayoutTest));
 }