Example showing alternate async measurement solution

client/html/src/NodeWrappingImplementation.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.
 
+// TODO(jacobr): we could write this method more efficiently if we wanted to
+// however performance isn't crucial as it is only called when a method is
+// called from an atypical context (e.g. measurement method called outside of
+// requestMeasurementFrame or dom manipulation called within
+// requestMeasurementFrame).
+bool _nodeInDocument(dom.Node node) {
+  return LevelDom.wrapNode(node)._inDocument;
+}
+
 class _ChildrenNodeList implements NodeList {
   // Raw node.
   final _node;
   final _childNodes;
 
   _ChildrenNodeList._wrap(var node)
     : _childNodes = node.childNodes,
       _node = node;
 
   List<Node> _toList() {
@@ skipping 62 matching lines @@
   void operator []=(int index, Node value) {
     _node.replaceChild(LevelDom.unwrap(value), _childNodes[index]);
   }
 
    void set length(int newLength) {
      throw new UnsupportedOperationException('');
    }
 
   /** @domName Node.appendChild */
   Node add(Node value) {
+    assert(!_inMeasurementFrame
+        || (!_nodeInDocument(_node) && !value._inDocument));
     _node.appendChild(LevelDom.unwrap(value));
     return value;
   }
 
   Node addLast(Node value) {
-    _node.appendChild(LevelDom.unwrap(value));
+     assert(!_inMeasurementFrame
+        || (!_nodeInDocument(_node) && !value._inDocument));
+   _node.appendChild(LevelDom.unwrap(value));
     return value;
   }
 
   Iterator<Node> iterator() {
     return _toList().iterator();
   }
 
   void addAll(Collection<Node> collection) {
+    assert(!_inMeasurementFrame || !_nodeInDocument(_node));
     for (Node node in collection) {
+      assert(!_inMeasurementFrame || !node._inDocument);
       _node.appendChild(LevelDom.unwrap(node));
     }
   }
 
   void sort(int compare(Node a, Node b)) {
     throw const UnsupportedOperationException('TODO(jacobr): should we impl?');
   }
 
   void copyFrom(List<Object> src, int srcStart, int dstStart, int count) {
     throw 'Not impl yet. todo(jacobr)';
@@ skipping 60 matching lines @@
   int indexOf(Node element, [int start = 0]) {
     return _Lists.indexOf(this, element, start, this.length);
   }
 
   int lastIndexOf(Node element, [int start = null]) {
     if (start === null) start = length - 1;
     return _Lists.lastIndexOf(this, element, start);
   }
 
   void clear() {
+    assert(!_inMeasurementFrame || !_nodeInDocument(_node));
     _node.textContent = '';
   }
 
   Node removeLast() {
+    assert(!_inMeasurementFrame || !_nodeInDocument(_node));
     final last = this.last();
     if (last != null) {
       _node.removeChild(LevelDom.unwrap(last));
     }
     return last;
   }
 
   Node last() {
     return LevelDom.wrapNode(_node.lastChild);
   }
 }
 
 class NodeWrappingImplementation extends EventTargetWrappingImplementation implements Node {
   NodeList _nodes;
 
   NodeWrappingImplementation._wrap(ptr) : super._wrap(ptr);
 
   void set nodes(Collection<Node> value) {
+    assert(!_inMeasurementFrame || !_inDocument);
     // Copy list first since we don't want liveness during iteration.
     List copy = new List.from(value);
     nodes.clear();
     nodes.addAll(copy);
   }
 
   NodeList get nodes() {
     if (_nodes === null) {
       _nodes = new _ChildrenNodeList._wrap(_ptr);
     }
     return _nodes;
   }
 
   Node get nextNode() => LevelDom.wrapNode(_ptr.nextSibling);
 
   Document get document() => LevelDom.wrapDocument(_ptr.ownerDocument);
 
   Node get parent() => LevelDom.wrapNode(_ptr.parentNode);
 
   Node get previousNode() => LevelDom.wrapNode(_ptr.previousSibling);
 
   String get text() => _ptr.textContent;
 
-  void set text(String value) { _ptr.textContent = value; }
+  void set text(String value) {
+    assert(!_inMeasurementFrame || !_inDocument);
+    _ptr.textContent = value;
+  }
 
   // New methods implemented.
   Node replaceWith(Node otherNode) {
+    assert(!_inMeasurementFrame || !_inDocument);
     try {
       _ptr.parentNode.replaceChild(LevelDom.unwrap(otherNode), _ptr);
     } catch(var e) {
       // TODO(jacobr): what should we return on failure?
     }
     return this;
   }
 
   Node remove() {
+    assert(!_inMeasurementFrame || !_inDocument);
     // TODO(jacobr): should we throw an exception if parent is already null?
     if (_ptr.parentNode !== null) {
       _ptr.parentNode.removeChild(_ptr);
     }
     return this;
   }
 
   /** @domName contains */
   bool contains(Node otherNode) {
     // TODO: Feature detect and use built in.
     while (otherNode != null && otherNode != this) {
       otherNode = otherNode.parent;
     }
     return otherNode == this;
   }
 
   // TODO(jacobr): remove when/if List supports a method similar to
   // insertBefore or we switch NodeList to implement LinkedList rather than
   // array.
   Node insertBefore(Node newChild, Node refChild) {
+    assert(!_inMeasurementFrame || !_inDocument);
     return LevelDom.wrapNode(_ptr.insertBefore(
         LevelDom.unwrap(newChild), LevelDom.unwrap(refChild)));
   }
 
   Node clone(bool deep) {
     return LevelDom.wrapNode(_ptr.cloneNode(deep));
   }
+
+  bool get _inDocument() => document.contains(this);
 }