Roll Observatory packages and add a roll script

packages/charted/lib/charts/src/chart_series_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 33 matching lines @@
   Iterable<int> get measures => _measures;
 
   set measureAxisIds(Iterable<String> value) => _measureAxisIds = value;
   Iterable<String> get measureAxisIds => _measureAxisIds;
 
   _measuresChanged(_) {
     if (_measures is! ObservableList) return;
     notifyChange(new ChartSeriesChangeRecord(this));
   }
 }