Roll Observatory packages and add a roll script

packages/charted/lib/charts/layout_renderers/layout_base_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 127 matching lines @@
         _valueStylesCache[row] = styles;
       }
     }
     return _valueStylesCache[row];
   }
 
   String colorForValue(int row, {bool isTail: false}) => isTail
       ? theme.getOtherColor()
       : theme.getColorForKey(row, _valueStateCache[row]);
 }