Attempting to stabilize node_model_test on IE9

tests/html/node_model_test.dart

 // Copyright (c) 2013, 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.
 
 library node_model_test;
 import 'dart:async';
 import 'dart:html';
 import '../../pkg/unittest/lib/unittest.dart';
 import '../../pkg/unittest/lib/html_config.dart';
 
+var stepDuration;
 Future get nextStep {
-  return new Future.delayed(new Duration());
+  return new Future.delayed(stepDuration);
 }
 
 class ModelTracker {
   Element element = new DivElement();
   List models = [];
 
   ModelTracker() {
     element.onModelChanged.listen((node) {
       models.add(node.model);
     });
   }
 
   void append(ModelTracker other) {
     element.append(other.element);
   }
 
   get model => element.model;
   void set model(value) {
     element.model = value;
   }
 
   void clearModel() {
     element.clearModel();
   }
+
+  void remove() {
+    element.remove();
+  }
 }
 
 main() {
   useHtmlConfiguration();
 
+  if (MutationObserver.supported) {
+    stepDuration = new Duration();
+  } else {
+    // Need to step after the tree update notifications, but on IE9 these may
+    // get polyfilled to use setTimeout(0). So use a longer timer to try to
+    // get a later callback.
+    stepDuration = new Duration(milliseconds: 15);
+  }
+
   test('basic top down', () {
     var a = new DivElement();
     var b = new SpanElement();
     var c = new DivElement();
     var d = new DivElement();
     var e = new DivElement();
     var model = {};
     var model2 = {};
     var model3 = {};
 
@@ skipping 40 matching lines @@
     }).then((_) {
       d.remove();
       c.append(d);
 
       return nextStep;
     }).then((_) {
       expect(d.model, model3);
 
       c.clearModel();
       expect(d.model, model2);
+
+      a.remove();
+      return nextStep;
     });
   });
 
   test('changes', () {
     var a = new ModelTracker();
     var b = new ModelTracker();
     var c = new ModelTracker();
     var d = new ModelTracker();
 
     var model = {};
@@ skipping 21 matching lines @@
       return nextStep;
     }).then((_) {
       c.model = cModel;
       expect(b.models, [model]);
       expect(c.models, [model, cModel]);
       expect(d.models, [model, cModel]);
 
       c.clearModel();
       expect(c.models, [model, cModel, model]);
       expect(d.models, [model, cModel, model]);
+
+      a.remove();
+      return nextStep;
     });
   });
 
   test('bottom up', () {
     var a = new ModelTracker();
     var b = new ModelTracker();
     var c = new ModelTracker();
     var d = new ModelTracker();
 
     var aModel = {};
     var cModel = {};
 
     c.append(d);
     c.model = cModel;
     b.append(c);
     a.append(b);
     a.model = aModel;
     document.body.append(a.element);
 
     return nextStep.then((_) {
       expect(a.models, [aModel]);
       expect(b.models, [aModel]);
       expect(c.models, [cModel]);
       expect(d.models, [cModel]);
+
+      a.remove();
+      return nextStep;
     });
   });
 }