Roll Observatory packages and add a roll script

packages/charted/lib/core/text_metrics/segmentation.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
 //
 
 library charted.core.text_metrics.segmentation;
 
@@ skipping 48 matching lines @@
   int previousType = 0;
   for (var iter = s.runes.iterator; iter.moveNext();) {
     int currentType = _typeForRune(iter.current);
     if (GRAPHEME_BREAK_TABLE[previousType * 12 + currentType] == 1) {
       indices.add(iter.rawIndex);
     }
     previousType = currentType;
   }
   return indices;
 }