pkg/unittest: Run tests in zones

sdk/lib/html/dartium/html_dartium.dart

Index: sdk/lib/html/dartium/html_dartium.dart
diff --git a/sdk/lib/html/dartium/html_dartium.dart b/sdk/lib/html/dartium/html_dartium.dart
index 19395c473387b6c0e7d16d943639917bb3005f99..52544f05df4bf0b0da12e75cba7a9a6cbff1a49d 100644
--- a/sdk/lib/html/dartium/html_dartium.dart
+++ b/sdk/lib/html/dartium/html_dartium.dart
@@ -38054,14 +38054,16 @@ class Platform {
 // BSD-style license that can be found in the LICENSE file.
 
 
-_wrapZone(callback) {
+_wrapZone(callback(arg)) {
   // For performance reasons avoid wrapping if we are in the root zone.
   if (Zone.current == Zone.ROOT) return callback;
+  if (callback == null) return null;
   return Zone.current.bindUnaryCallback(callback, runGuarded: true);
 }
 
-_wrapBinaryZone(callback) {
+_wrapBinaryZone(callback(arg1, arg2)) {
   if (Zone.current == Zone.ROOT) return callback;
+  if (callback == null) return null;
   return Zone.current.bindBinaryCallback(callback, runGuarded: true);
 }