Roll Observatory packages and add a roll script

packages/stack_trace/lib/src/utils.dart

 // Copyright (c) 2013, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 library stack_trace.src.utils;
 
 /// Returns [string] with enough spaces added to the end to make it [length]
 /// characters long.
 String padRight(String string, int length) {
   if (string.length >= length) return string;
@@ skipping 16 matching lines @@
       if (element is List) {
         helper(element);
       } else {
         result.add(element);
       }
     }
   }
   helper(nested);
   return result;
 }