Removed const from classes arrays in Observatory

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

 // Copyright (c) 2014, 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.
 
 library heap_map_element;
 
 import 'dart:async';
 import 'dart:html';
 import 'dart:math';
 import 'package:observatory/models.dart' as M;
@@ skipping 96 matching lines @@
         ..children = [
           new NavTopMenuElement(queue: _r.queue),
           new NavVMMenuElement(_vm, _events, queue: _r.queue),
           new NavIsolateMenuElement(_isolate, _events, queue: _r.queue),
           new NavMenuElement('heap map', last: true,
               link: Uris.heapMap(_isolate), queue: _r.queue),
           new NavRefreshElement(queue: _r.queue)
             ..onRefresh.listen((_) => _refresh()),
           new NavNotifyElement(_notifications, queue: _r.queue)
         ],
-      new DivElement()..classes = const ['content-centered-big']
+      new DivElement()..classes = ['content-centered-big']
         ..children = [
           new HeadingElement.h2()..text = _status,
           new HRElement(),
         ],
         new DivElement()..classes = ['flex-row']
           ..children = [_canvas]
     ];
   }
 
   // Encode color as single integer, to enable using it as a map key.
@@ skipping 187 matching lines @@
 
   // The row-major index of this pixel.
   int get index => _dataIndex ~/ NUM_COLOR_COMPONENTS;
 }
 
 class ObjectInfo {
   final address;
   final size;
   ObjectInfo(this.address, this.size);
 }