Example showing alternate async measurement solution

client/html/src/DocumentWrappingImplementation.dart

Index: client/html/src/DocumentWrappingImplementation.dart
diff --git a/client/html/src/DocumentWrappingImplementation.dart b/client/html/src/DocumentWrappingImplementation.dart
index 8db883f8b49694e1091e7478cf6acf8e77b39f92..0ff1802cde909bef23db141c8f3c05c1b8c35a18 100644
--- a/client/html/src/DocumentWrappingImplementation.dart
+++ b/client/html/src/DocumentWrappingImplementation.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.
 
@@ -82,10 +82,9 @@ class DocumentWrappingImplementation extends ElementWrappingImplementation imple
   String get webkitVisibilityState() => _documentPtr.webkitVisibilityState;
 
   /** @domName caretRangeFromPoint */
-  Future<Range> caretRangeFromPoint([int x = null, int y = null]) {
-    return _createMeasurementFuture(
-        () => LevelDom.wrapRange(_documentPtr.caretRangeFromPoint(x, y)),
-        new Completer<Range>());
+  Range caretRangeFromPoint([int x = null, int y = null]) {
+    assert(_inMeasurementFrame);
+    return LevelDom.wrapRange(_documentPtr.caretRangeFromPoint(x, y));
   }
 
   /** @domName createEvent */
@@ -94,14 +93,14 @@ class DocumentWrappingImplementation extends ElementWrappingImplementation imple
   }
 
   /** @domName elementFromPoint */
-  Future<Element> elementFromPoint([int x = null, int y = null]) {
-    return _createMeasurementFuture(
-        () => LevelDom.wrapElement(_documentPtr.elementFromPoint(x, y)),
-        new Completer<Element>());
+  Element elementFromPoint([int x = null, int y = null]) {
+    assert(_inMeasurementFrame);
+    return LevelDom.wrapElement(_documentPtr.elementFromPoint(x, y));
   }
 
   /** @domName execCommand */
   bool execCommand([String command = null, bool userInterface = null, String value = null]) {
+    assert(!_inMeasurementFrame);
     return _documentPtr.execCommand(command, userInterface, value);
   }
 
@@ -140,7 +139,10 @@ class DocumentWrappingImplementation extends ElementWrappingImplementation imple
   String get manifest() => _ptr.manifest;
 
   /** @domName HTMLHtmlElement.manifest */
-  void set manifest(String value) { _ptr.manifest = value; }
+  void set manifest(String value) {
+    assert(!_inMeasurementFrame);
+    _ptr.manifest = value;
+  }
 
   DocumentEvents get on() {
     if (_on === null) {