Update charted to 0.4.8 and roll

packages/charted/lib/charts/data_transformers/aggregation_transformer.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;
 
 /// Transforms the ChartData based on the specified dimension columns and facts
 /// columns indices. The values in the facts columns will be aggregated by the
 /// tree hierarchy generated by the dimension columns.  Expand and Collapse
 /// methods may be called to display different levels of aggregation.
 ///
 /// The output ChartData produced by transform() will contain only columns in the
 /// original ChartData that were specified in dimensions or facts column indices.
 /// The output column will be re-ordered first by the indices specified in the
 /// dimension column indices then by the facts column indices.  The data in the
 /// cells of each row will also follow this rule.
-class AggregationTransformer extends ChangeNotifier
+class AggregationTransformer extends Observable
     implements ChartDataTransform, ChartData {
   static const String AGGREGATION_TYPE_SUM = 'sum';
   static const String AGGREGATION_TYPE_MIN = 'min';
   static const String AGGREGATION_TYPE_MAX = 'max';
   static const String AGGREGATION_TYPE_VALID = 'valid';
   final SubscriptionsDisposer _dataSubscriptions = new SubscriptionsDisposer();
   final Set<List> _expandedSet = new Set();
   List<ChartColumnSpec> columns;
   ObservableList<List> rows = new ObservableList<List>();
   List<int> _dimensionColumnIndices;
@@ skipping 169 matching lines @@
     _expandAllDimension = false;
     _expandedSet.clear();
   }
 
   /// Tests if specific dimension is expanded.
   bool _isExpanded(List dimension) {
     Function eq = const ListEquality().equals;
     return _expandedSet.any((e) => eq(e, dimension));
   }
 }