Example showing alternate async measurement solution

client/view/SliderMenu.dart

-// 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.
 
 typedef void SelectHandler(String menuText);
 
 /**
  * This implements a horizontal menu bar with a sliding triangle arrow
  * that points at the currently selected item.
  */
 class SliderMenu extends View {
@@ skipping 136 matching lines @@
       selectItem(result, animate);
     }
   }
 
   /**
    * animate - if true, then animate the movement of the triangle slider
    */
   void updateIndicator(bool animate) {
     if (selectedItem != null) {
       // calculate where we want to put the triangle
-      selectedItem.rect.then((ElementRect rect) {
-        num x = rect.offset.left +
-            rect.offset.width / 2 - TRIANGLE_WIDTH / 2;
-        _moveIndicator(x, animate);
+      window.requestMeasurementFrame(() {
+        final offsetRect = selectedItem.rect.offset;
+        num x = offsetRect.left + offsetRect.width / 2 - TRIANGLE_WIDTH / 2;
+        return () { _moveIndicator(x, animate); };
       });
     } else {
       _moveIndicator(0, animate);
     }
   }
 
   void _moveIndicator(num x, bool animate) {
     // find the slider filler (the div element to the left of the
     // triangle) set its width the push the triangle to where we want it.
     String duration = animate ? '.3s' : '0s';
     final triangle = node.query('.sm-triangle');
     triangle.style.transitionDuration = duration;
     FxUtil.setWebkitTransform(triangle, x, 0);
   }
 }