Removed const from classes arrays in Observatory

runtime/observatory/lib/src/elements/object_view.dart

 // Copyright (c) 2013, 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/models.dart' as M;
 import 'package:observatory/src/elements/context_ref.dart';
 import 'package:observatory/src/elements/curly_block.dart';
 import 'package:observatory/src/elements/helpers/rendering_scheduler.dart';
@@ skipping 107 matching lines @@
           new NavIsolateMenuElement(_isolate, _events, queue: _r.queue),
           new NavMenuElement('object', last: true, queue: _r.queue),
           new NavRefreshElement(queue: _r.queue)
               ..onRefresh.listen((e) async {
                 e.element.disabled = true;
                 _object = await _objects.get(_isolate, _object.id);
                 _r.dirty();
               }),
           new NavNotifyElement(_notifications, queue: _r.queue)
         ],
-      new DivElement()..classes = const ['content-centered-big']
+      new DivElement()..classes = ['content-centered-big']
         ..children = [
           new HeadingElement.h2()..text = 'Object',
           new HRElement(),
           new ObjectCommonElement(_isolate, _object, _retainedSizes,
                                   _reachableSizes, _references, _retainingPaths,
                                   _instances, queue: _r.queue),
           new HRElement(),
           new ViewFooterElement(queue: _r.queue)
         ]
     ];
   }
 }