Added missing content to nav-top-menu

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

 // Copyright (c) 2015, 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.
 
 // 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 'dart:math' as Math;
 import 'package:observatory/models.dart' as M;
 import 'package:observatory/src/elements/class_ref.dart';
 import 'package:observatory/src/elements/containers/virtual_tree.dart';
 import 'package:observatory/src/elements/helpers/any_ref.dart';
 import 'package:observatory/src/elements/helpers/nav_bar.dart';
 import 'package:observatory/src/elements/helpers/nav_menu.dart';
 import 'package:observatory/src/elements/helpers/rendering_scheduler.dart';
 import 'package:observatory/src/elements/helpers/tag.dart';
-import 'package:observatory/src/elements/helpers/uris.dart';
 import 'package:observatory/src/elements/nav/isolate_menu.dart';
 import 'package:observatory/src/elements/nav/notify.dart';
 import 'package:observatory/src/elements/nav/refresh.dart';
 import 'package:observatory/src/elements/nav/top_menu.dart';
 import 'package:observatory/src/elements/nav/vm_menu.dart';
 import 'package:observatory/utils.dart';
 
 enum HeapSnapshotTreeMode {
   dominatorTree,
   groupByClass
@@ skipping 373 matching lines @@
                 selected: _mode == mode)
               ..text = modeToString(mode);
           }).toList(growable: false)
         ..onChange.listen((_) {
             _mode = HeapSnapshotTreeMode.values[s.selectedIndex];
             _r.dirty();
           })
     ];
   }
 }