Second round of deprecation removal.

tests/html/mutationobserver_test.dart

Index: tests/html/mutationobserver_test.dart
diff --git a/tests/html/mutationobserver_test.dart b/tests/html/mutationobserver_test.dart
index f73f2a5bdea9293ac14074c02898b6f52cf5151c..0af69c50bb8f882a9c856eb3891ccccb3fea8204 100644
--- a/tests/html/mutationobserver_test.dart
+++ b/tests/html/mutationobserver_test.dart
@@ -99,15 +99,5 @@ main() {
         div1.append(div2);
       }, expectation);
     });
-
-    test('mutation event', () {
-      // Bug 8076 that not all optional params are optional in Dartium.
-      var event = new MutationEvent('something', prevValue: 'prev',
-          newValue: 'new', attrName: 'attr');
-      expect(event is MutationEvent, isTrue);
-      expect(event.prevValue, 'prev');
-      expect(event.newValue, 'new');
-      expect(event.attrName, 'attr');
-    });
   });
 }