Execute callbacks from JS in the correct zone

tests/html/js_test.dart

Index: tests/html/js_test.dart
diff --git a/tests/html/js_test.dart b/tests/html/js_test.dart
index 081ab0270576c4bd3a86d22885eae90a21c73fba..04b5a29e48f2568952d4f229a932442955cbf886 100644
--- a/tests/html/js_test.dart
+++ b/tests/html/js_test.dart
@@ -659,6 +659,20 @@ main() {
       context.deleteProperty('callback');
     });
 
+    test('invoke Dart callback from JS in a Zone', () {
+      expect(() => context.callMethod('invokeCallback'), throws);
+
+      var childZone = Zone.current.fork();
+      childZone.run(() {
+        context['callback'] = () {
+          expect(Zone.current, childZone);
+        };
+      });
+      context.callMethod('invokeCallback');
+
+      context.deleteProperty('callback');
+    });
+
     test('callback as parameter', () {
       expect(context.callMethod('getTypeOf', [context['razzle']]),
           equals("function"));