Roll Observatory packages and add a roll script

packages/charted/lib/core/utils/bidi_formatter.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.core.utils;
 
@@ skipping 36 matching lines @@
     } else if (_digitsRegExp.hasMatch(token)) {
       hasWeaklyLtr = true;
     }
   }
   if (total == 0) {
     return hasWeaklyLtr ? TextDirection.LTR : TextDirection.UNKNOWN;
   } else {
     return rtlCount > 0.4 * total ? TextDirection.RTL : TextDirection.LTR;
   }
 }