Roll Observatory packages and add a roll script

packages/charted/lib/charts/data_transformers/aggregation.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;
 
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         });
         if (match) {
           return current[i];
         }
       }
     } else {
       return current[part];
     }
   });
 }