Roll Observatory packages and add a roll script

packages/source_maps/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.
 
 /// Utilities that shouldn't be in this package.
 library source_maps.utils;
 
 /// Find the first entry in a sorted [list] that matches a monotonic predicate.
 /// Given a result `n`, that all items before `n` will not match, `n` matches,
 /// and all items after `n` match too. The result is -1 when there are no
 /// items, 0 when all items match, and list.length when none does.
 // TODO(sigmund): remove this function after dartbug.com/5624 is fixed.
 int binarySearch(List list, bool matches(item)) {
   if (list.length == 0) return -1;
   if (matches(list.first)) return 0;
   if (!matches(list.last)) return list.length;
 
   int min = 0;
   int max = list.length - 1;
   while (min < max) {
     var half = min + ((max - min) ~/ 2);
     if (matches(list[half])) {
       max = half;
     } else {
       min = half + 1;
     }
   }
   return max;
 }