Removed const from classes arrays in Observatory

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();
@@ skipping 59 matching lines @@
 
  @override
   detached() {
     super.detached();
     _r.disable(notify: true);
     children = const [];
     _onScrollSubscription.cancel();
     _onResizeSubscription.cancel();
   }
 
-  final DivElement _header = new DivElement()..classes = const ['header'];
-  final DivElement _scroller = new DivElement()..classes = const ['scroller'];
-  final DivElement _shifter = new DivElement()..classes = const ['shifter'];
+  final DivElement _header = new DivElement()..classes = ['header'];
+  final DivElement _scroller = new DivElement()..classes = ['scroller'];
+  final DivElement _shifter = new DivElement()..classes = ['shifter'];
 
   dynamic getItemFromElement(HtmlElement element) {
     final el_index = _shifter.children.indexOf(element);
     if (el_index < 0) {
       return null;
     }
     final item_index =
       _top + el_index - (_shifter.children.length * _inverse_preload).floor();
     if (0 <= item_index && item_index < items.length) {
       return _items[item_index];
@@ skipping 86 matching lines @@
   }
 
   void _onResize(_) {
     final newHeight = getBoundingClientRect().height;
     if (newHeight > _height) {
       _height = newHeight;
       _r.dirty();
     }
   }
 }