Update charted to 0.4.8 and roll

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;
 
-class DefaultChartSeriesImpl extends ChangeNotifier implements ChartSeries {
+class DefaultChartSeriesImpl extends Observable implements ChartSeries {
   final String name;
 
   Iterable<String> _measureAxisIds;
   Iterable<int> _measures;
   ChartRenderer _renderer;
 
   SubscriptionsDisposer _disposer = new SubscriptionsDisposer();
 
   DefaultChartSeriesImpl(this.name, Iterable<int> measures, this._renderer,
       Iterable<String> measureAxisIds) {
@@ skipping 25 matching lines @@
     _measureAxisIds = value;
   }
 
   Iterable<String> get measureAxisIds => _measureAxisIds;
 
   void _measuresChanged(List<ListChangeRecord> _) {
     if (_measures is! ObservableList) return;
     notifyChange(new ChartSeriesChangeRecord(this));
   }
 }