Roll Observatory packages and add a roll script

packages/collection/lib/iterable_zip.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.
 
 /**
  * Zipping multiple iterables into one iterable of tuples of values.
  */
 library dart.pkg.collection.iterable_zip;
 
 import "dart:collection" show IterableBase;
@@ skipping 39 matching lines @@
     }
     _current = new List(_iterators.length);
     for (int i = 0; i < _iterators.length; i++) {
       _current[i] = _iterators[i].current;
     }
     return true;
   }
 
   List get current => _current;
 }