Update charted to 0.4.8 and roll

packages/charted/lib/charts/src/chart_data_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 DefaultChartDataImpl extends ChangeNotifier implements ChartData {
+class DefaultChartDataImpl extends Observable implements ChartData {
   List<ChartColumnSpec> _columns;
   List<List> _rows;
 
   bool _hasObservableRows = false;
   SubscriptionsDisposer _disposer = new SubscriptionsDisposer();
 
   DefaultChartDataImpl(
-      Iterable<ChartColumnSpec> columns, Iterable<Iterable> rows) {
-    this.columns = new List<ChartColumnSpec>.from(columns);
-    var rowsList = new List.from(rows);
-    this.rows = new List<List>.generate(
-        rowsList.length, (i) => new List.from(rowsList[i]));
+      Iterable<ChartColumnSpec> columns, List<List> rows) {
+    this.columns = columns;
+    this.rows = rows;
   }
 
   set columns(Iterable<ChartColumnSpec> value) {
     assert(value != null);
 
     // Create a copy of columns.  We do not currently support
     // changes to the list of columns.  Any changes to the spec
     // will be applied at the next ChartBase.draw();
     this._columns = new List<ChartColumnSpec>.from(value);
   }
@@ skipping 100 matching lines @@
         strBuffer.write(' ' * lengthDiff + ' ${data} |');
 
         if (i == row.length - 1) {
           strBuffer.write('\n' + '-' * totalLength + '\n');
         }
       }
     }
     return strBuffer.toString();
   }
 }