Wrapping leaf nodes in non polymer elements

runtime/observatory/lib/src/elements/helpers/rendering_queue.dart

+// Copyright (c) 2016, 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.
+
+import 'dart:html';
+import 'dart:collection';
+import 'dart:async';
+
+abstract class RenderingTask {
+  void render();
+}
+
+abstract class RenderingBarrier {
+  Future<num> get next;
+}
+
+class NextAnimationFrameBarrier implements RenderingBarrier {
+  Future<num> get next => window.animationFrame;
+}
+
+class RenderingQueue {
+  final RenderingBarrier _barrier;
+  final Queue<RenderingTask> _queue = new Queue<RenderingTask>();
+
+  bool get isEmpty => _queue.isEmpty;
+  bool get isNotEmpty => _queue.isNotEmpty;
+
+  RenderingQueue() : this.fromBarrier(new NextAnimationFrameBarrier());
+
+  RenderingQueue.fromBarrier(this._barrier);
+
+  void enqueue(RenderingTask r) {
+    assert(r != null);
+    if (isEmpty) _render();
+    _queue.addLast(r);
+  }
+
+  Future _render() async {
+    await _barrier.next;
+    while (_queue.isNotEmpty) {
+      _queue.removeFirst().render();
+    }
+  }
+}