Add cross-origin test with credentials.

pkg/unittest/lib/html_individual_config.dart

Index: pkg/unittest/lib/html_individual_config.dart
diff --git a/pkg/unittest/lib/html_individual_config.dart b/pkg/unittest/lib/html_individual_config.dart
index 95e051478bc48fa04d8169c3341a4b594d9c5391..ae67d32989a0337ea6b535057bfb0e7ffd90283b 100644
--- a/pkg/unittest/lib/html_individual_config.dart
+++ b/pkg/unittest/lib/html_individual_config.dart
@@ -41,3 +41,7 @@ class HtmlIndividualConfiguration extends htmlconfig.HtmlConfiguration {
 void useHtmlIndividualConfiguration([bool isLayoutTest = false]) {
   unittest.configure(new HtmlIndividualConfiguration(isLayoutTest));
 }
+
+int getCrossOriginPortNumber() {

[Siggi Cherem (dart-lang), 2013/01/04 01:49:43]

style nit: use =>
int get crossOriginPort => htmlconfig.crossOriginPort;

but I guess if this moves out of unittest, then you might not need this anymore
=)

[Emily Fortuna, 2013/01/04 23:26:54]

Done.

+  return htmlconfig.getCrossOriginPortNumber();
+}