Add cross-origin test with credentials.

tests/html/xhr_cross_origin_test.dart

Index: tests/html/xhr_cross_origin_test.dart
diff --git a/tests/html/xhr_cross_origin_test.dart b/tests/html/xhr_cross_origin_test.dart
index d39af2c85e388bcfdb6e6e60f0f352ff50b9f429..c7993e6add777ca6c8f5a1b505410c5a59d256a9 100644
--- a/tests/html/xhr_cross_origin_test.dart
+++ b/tests/html/xhr_cross_origin_test.dart
@@ -39,4 +39,14 @@ main() {
       expect(data, isMap);
     }));
   });
+
+  test('XHR.getWithCredentials Cross-domain', () {
+    var url = "http://localhost:9876/tests/html/xhr_cross_origin_data.txt";
+    new HttpRequest.getWithCredentials(url, expectAsync1((xhr) {
+      var data = JSON.parse(xhr.response);
+      expect(data, contains('feed'));
+      expect(data['feed'], contains('entry'));
+      expect(data, isMap);
+    }));
+  });
 }