Example showing alternate async measurement solution

client/html/src/WindowWrappingImplementation.dart

Index: client/html/src/WindowWrappingImplementation.dart
diff --git a/client/html/src/WindowWrappingImplementation.dart b/client/html/src/WindowWrappingImplementation.dart
index a4f8b9c954f10c66c1af42d722bbbc12e38daf6d..bfa7af7541fbc2e4970b2c0f5d265c7aa643cebb 100644
--- a/client/html/src/WindowWrappingImplementation.dart
+++ b/client/html/src/WindowWrappingImplementation.dart
@@ -1,4 +1,4 @@
-// Copyright (c) 2011, the Dart project authors.  Please see the AUTHORS file
+// 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.
 
@@ -803,6 +803,7 @@ class WindowWrappingImplementation extends EventTargetWrappingImplementation imp
   }
 
   Point webkitConvertPointFromNodeToPage([Node node = null, Point p = null]) {
+    assert(_inMeasurementFrame);
     if (node === null) {
       if (p === null) {
         return LevelDom.wrapPoint(_ptr.webkitConvertPointFromNodeToPage());
@@ -818,6 +819,7 @@ class WindowWrappingImplementation extends EventTargetWrappingImplementation imp
   }
 
   Point webkitConvertPointFromPageToNode([Node node = null, Point p = null]) {
+    assert(_inMeasurementFrame);
     if (node === null) {
       if (p === null) {
         return LevelDom.wrapPoint(_ptr.webkitConvertPointFromPageToNode());
@@ -836,10 +838,12 @@ class WindowWrappingImplementation extends EventTargetWrappingImplementation imp
     return _ptr.webkitRequestAnimationFrame(callback, LevelDom.unwrap(element));
   }
 
-  void requestLayoutFrame(TimeoutHandler callback) {
+  void requestMeasurementFrame(MeasurementCallback callback) {
     _addMeasurementFrameCallback(callback);
   }
 
+  bool get inMeasurementFrame() => _inMeasurementFrame;
+
   WindowEvents get on() {
     if (_on === null) {
       _on = new WindowEventsImplementation._wrap(_ptr);