Alternative fix for the js-interop crash.

tests/html/js_typed_interop_side_cast_test.dart

Index: tests/html/js_typed_interop_side_cast_test.dart
diff --git a/tests/html/fontface_test.dart b/tests/html/js_typed_interop_side_cast_test.dart
similarity index 50%
copy from tests/html/fontface_test.dart
copy to tests/html/js_typed_interop_side_cast_test.dart
index 8247a8a268e7e5c28401c3aed9a42b625ae7c77a..fb2bae789997a17574c070b6cfaa5520d3d62637 100644
--- a/tests/html/fontface_test.dart
+++ b/tests/html/js_typed_interop_side_cast_test.dart
@@ -2,21 +2,33 @@
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
-library fontface_test;
+library js_typed_interop_anonymous2_test;
 
+import 'dart:html';
+import 'dart:js' as js;
+
+import 'package:js/js.dart';
 import 'package:unittest/unittest.dart';
 import 'package:unittest/html_config.dart';
 
-import 'dart:html';
+@JS() @anonymous
+class A {
+  external int get x;
+  external factory A({int x});
+}
+
+@JS() @anonymous
+class B {
+  external int get x;
+  external factory B({int x});
+}
 
 main() {
   useHtmlConfiguration();
 
-  test("Creation with parameters", () {
-    var font =
-        new FontFace('Ahem', 'url(Ahem.ttf)', {'variant': 'small-caps'});
-    expect(font is FontFace, isTrue);
-    expect(font.family, 'Ahem');
-    expect(font.variant, 'small-caps');
+  test('side-casts are allowed', () {
+    var a = new A(x: 3);
+    B b = a;
+    expect(b.x, equals(3));
   });
 }