Update charted to 0.4.8 and roll

packages/charted/lib/charts/src/chart_data_impl.dart

Index: packages/charted/lib/charts/src/chart_data_impl.dart
diff --git a/packages/charted/lib/charts/src/chart_data_impl.dart b/packages/charted/lib/charts/src/chart_data_impl.dart
index 2dc6ed0f65cb02584782dccb80f79c0d8f9b4b93..08ef87e388bea80ff20889935f47d43e0b6fbd7d 100644
--- a/packages/charted/lib/charts/src/chart_data_impl.dart
+++ b/packages/charted/lib/charts/src/chart_data_impl.dart
@@ -8,7 +8,7 @@
 
 part of charted.charts;
 
-class DefaultChartDataImpl extends ChangeNotifier implements ChartData {
+class DefaultChartDataImpl extends Observable implements ChartData {
   List<ChartColumnSpec> _columns;
   List<List> _rows;
 
@@ -16,11 +16,9 @@ class DefaultChartDataImpl extends ChangeNotifier implements ChartData {
   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) {