Revert "Use Timer and not AnimationFrame during Observatory UI tests"

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';
 
 /// A generic rendering task that can be scheduled.
 abstract class RenderingTask {
@@ skipping 19 matching lines @@
 
   Future<num> get next => _stream.stream.first;
 
   /// Trigger the next barrier with an optional numer of ms elapsed.
   void triggerRenderingBarrier({num step: 20}) {
     assert(step != null);
     _stream.add(_ms += step);
   }
 }
 
-/// MOCK synchronization system for timed barrier triggering.
-class TimedRenderingBarrier implements RenderingBarrier {
-  final StreamController<num> _stream = new StreamController<num>.broadcast();
-  num _ms = 0;
-
-  Future<num> get next => _stream.stream.first;
-
-  TimedRenderingBarrier({num milliseconds: 1}) {
-    assert(milliseconds != null);
-    assert(milliseconds > 0);
-    new Timer.periodic(new Duration(milliseconds: milliseconds), (Timer t) {
-      _stream.add(_ms += milliseconds);
-    });
-  }
-}
-
 /// RenderingTask queuing and synchronization system.
 class RenderingQueue {
   final RenderingBarrier _barrier;
   final Queue<RenderingTask> _queue = new Queue<RenderingTask>();
 
   bool get isEmpty => _queue.isEmpty;
   bool get isNotEmpty => _queue.isNotEmpty;
 
   /// Creates a RenderingQueue with the default synchronization barrier.
   RenderingQueue() : this.fromBarrier(new NextAnimationFrameBarrier());
@@ skipping 13 matching lines @@
     _queue.addLast(r);
   }
 
   Future _render() async {
     await _barrier.next;
     while (_queue.isNotEmpty) {
       _queue.removeFirst().render();
     }
   }
 }