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 68d6fc36ace8eee6f6b21841a9325286af266d46..f960a2caefd5e14fd2bf2dfb30d2dc25e0c6bc35 100644
--- a/sdk/lib/html/dartium/html_dartium.dart
+++ b/sdk/lib/html/dartium/html_dartium.dart
@@ -18820,10 +18820,7 @@ class MutationObserver extends NativeFieldWrapperClass1 {
   }
 
   factory MutationObserver(MutationCallback callback) =>
-      new MutationObserver._((changes, observer) {
-        _wrapZone(() {
-            callback(changes, observer);
-          });
+      new MutationObserver._(_wrapBinaryZone(callback));
         });
 }
 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
@@ -35239,6 +35236,11 @@ _wrapZone(callback) {
   return Zone.current.bindUnaryCallback(callback, runGuarded: true);
 }
 
+_wrapBinaryZone(callback) {
+  if (Zone.current == Zone.ROOT) return callback;
+  return Zone.current.bindBinaryCallback(callback, runGuarded: true);
+}
+
 Element query(String selector) => document.query(selector);
 ElementList queryAll(String selector) => document.queryAll(selector);
 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file