Roll Observatory packages and add a roll script

packages/charted/lib/charts/chart_area.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;
 
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   /// Sizes of axes by orientation.
   /// Only valid on [CartesianArea], null otherwise.
   Map<String, Rect> get axes;
 
   /// Size of render area.
   Rect get renderArea => new Rect();
 
   /// Size of chart area.
   Rect get chartArea => new Rect();
 }