Updated charted DEP to 0.4.X

packages/charted/lib/charts/src/chart_events_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 DefaultChartEventImpl implements ChartEvent {
   @override
   final ChartArea area;
 
   @override
   final ChartSeries series;
 
   @override
-  final MouseEvent source;
+  final Event source;
 
   @override
   final int column;
 
   @override
   final int row;
 
   @override
   final num value;
 
   @override
   num chartX = 0;
 
   @override
   num chartY = 0;
 
   DefaultChartEventImpl(this.source, this.area,
       [this.series, this.row, this.column, this.value]) {
     var hostRect = area.host.getBoundingClientRect(),
         left =
         area.config.isRTL ? area.theme.padding.end : area.theme.padding.start;
-    if (source != null) {
-      chartX = source.client.x - hostRect.left - left;
-      chartY = source.client.y - hostRect.top - area.theme.padding.top;
+    if (source is MouseEvent) {
+      MouseEvent mouseSource = source;
+      chartX = mouseSource.client.x - hostRect.left - left;
+      chartY = mouseSource.client.y - hostRect.top - area.theme.padding.top;
     }
   }
 }