Build Observatory with runtime

runtime/observatory/lib/src/app/view_model.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.
 
 part of app;
 
 abstract class TableTreeRow extends Observable {
   final TableTreeRow parent;
   @observable final int depth;
   @observable final List<TableTreeRow> children = new List<TableTreeRow>();
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     if (column != _sortColumnIndex) {
       return columns[column].label + '\u2003';
     }
     return columns[column].label + (_sortDescending ? arrowUp : arrowDown);
   }
 
   dynamic getValue(int row, int column) {
     return rows[row].values[column];
   }
 }