Fix scheduleImmediate in Dartium.

tools/dom/src/native_DOMImplementation.dart

 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // 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.
 
 part of html;
 
 class _ConsoleVariables {
   Map<String, Object> _data = new Map<String, Object>();
 
   /**
@@ skipping 519 matching lines @@
     ((int milliSeconds, void callback(Timer time), bool repeating) =>
   throw new UnimplementedError("Timers on background isolates "
                                "are not supported in the browser"));
 
 class _ScheduleImmediateHelper {
   MutationObserver _observer;
   final DivElement _div = new DivElement();
   Function _callback;
 
   _ScheduleImmediateHelper() {
-    // Mutation events get fired as soon as the current event stack is unwound
-    // so we just make a dummy event and listen for that.
-    _observer = new MutationObserver(_handleMutation);
-    _observer.observe(_div, attributes: true);
+    // Run in the root-zone as the DOM callback would otherwise execute in the
+    // current zone.
+    Zone.ROOT.run(() {
+      // Mutation events get fired as soon as the current event stack is unwound
+      // so we just make a dummy event and listen for that.
+      _observer = new MutationObserver(_handleMutation);
+      _observer.observe(_div, attributes: true);
+    });
   }
 
   void _schedule(callback) {
     if (_callback != null) {
       throw new StateError(
           'Only one immediate callback can be scheduled at once');
     }
     _callback = callback;
     // Toggle it to trigger the mutation event.
     _div.hidden = !_div.hidden;
@@ skipping 13 matching lines @@
   _scheduleImmediateHelper._schedule(callback);
 };
 
 get _pureIsolateScheduleImmediateClosure => ((void callback()) =>
   throw new UnimplementedError("scheduleMicrotask in background isolates "
                                "are not supported in the browser"));
 
 void _initializeCustomElement(Element e) {
   _Utils.initializeCustomElement(e);
 }