Roll Observatory packages and add a roll script

packages/charted/lib/charts/cartesian_renderers/line_chart_renderer.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;
 
@@ skipping 255 matching lines @@
     if (area.state != null &&
         area.state.preview == int.parse(e.dataset['column'])) {
       area.state.preview = null;
     }
     if (mouseOutController != null && e.tagName == 'circle') {
       mouseOutController.add(new DefaultChartEventImpl(
           scope.event, area, series, _savedOverRow, _savedOverColumn, d));
     }
   }
 }