Converted Observatory class-tree element

runtime/observatory/lib/src/elements/containers/virtual_collection.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:async';
 import 'dart:html';
 import 'package:observatory/src/elements/helpers/rendering_scheduler.dart';
 import 'package:observatory/src/elements/helpers/tag.dart';
 
 typedef HtmlElement VirtualCollectionCreateCallback();
 typedef void VirtualCollectionUpdateCallback(HtmlElement el, dynamic item,
     int index);
 
 class VirtualCollectionElement extends HtmlElement implements Renderable {
   static const tag =
       const Tag<VirtualCollectionElement>('virtual-collection');
 
   RenderingScheduler<VirtualCollectionElement> _r;
 
   Stream<RenderedEvent<VirtualCollectionElement>> get onRendered =>
       _r.onRendered;
 
   VirtualCollectionCreateCallback _create;
   VirtualCollectionUpdateCallback _update;
   double _itemHeight;
   int _top;
-  int _height;
+  double _height;
   List _items;
   StreamSubscription _onScrollSubscription;
   StreamSubscription _onResizeSubscription;
 
   List get items => _items;
 
   set items(Iterable value) {
     _items = new List.unmodifiable(value);
     _r.dirty();
   }
@@ skipping 111 matching lines @@
          _shifter.children.length * _inverse_preload * _itemHeight) {
       _r.dirty();
     }
   }
 
   void _onResize(_) {
     _height = getBoundingClientRect().height;
     _r.dirty();
   }
 }