Example showing alternate async measurement solution

client/html/src/Element.dart

Index: client/html/src/Element.dart
diff --git a/client/html/src/Element.dart b/client/html/src/Element.dart
index ea5a3de313e826245c101113a4754df92a1f1ab9..7236491115dd067adcff143e0ba9b898d5bd1a6b 100644
--- a/client/html/src/Element.dart
+++ b/client/html/src/Element.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.
 
@@ -8,10 +8,6 @@ interface ElementList extends List<Element> {
   // TODO(jacobr): add insertAt
 }
 
-class DeferredElementRect {
-  // TODO(jacobr)
-}
-
 interface ElementEvents extends Events {
   EventListenerList get abort();
   EventListenerList get beforeCopy();
@@ -185,11 +181,14 @@ interface Element extends Node /*, common.NodeSelector, common.ElementTraversal
 
   bool matchesSelector([String selectors]);
 
-  Future<ElementRect> get rect();
+  /** Only access members when [window.inMeasurementFrame] is true. */
+  ElementRect get rect();
 
-  Future<CSSStyleDeclaration> get computedStyle();
+  /** Only call when [window.inMeasurementFrame] is true. */
+  CSSStyleDeclaration get computedStyle();
 
-  Future<CSSStyleDeclaration> getComputedStyle(String pseudoElement);
+  /** Only call when [window.inMeasurementFrame] is true. */
+  CSSStyleDeclaration getComputedStyle(String pseudoElement);
 
   ElementEvents get on();