Roll Observatory packages and add a roll script

packages/charted/lib/charts/src/chart_state_impl.dart

 //
 // Copyright 2014 Google Inc. All rights reserved.
 //
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file or at
 // https://developers.google.com/open-source/licenses/bsd
 //
 
 part of charted.charts;
 
@@ skipping 113 matching lines @@
       var item = new Pair(column, row);
       highlights.remove(item);
       notifyChange(new ChartHighlightChangeRecord(remove: item));
     }
     return false;
   }
 
   bool isHighlighted(int column, int row) =>
       highlights.any((x) => x.first == column && x.last == row);
 }