Roll Observatory packages and add a roll script

polymer_expressions/lib/filter.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 polymer_expressions.filter;
-
-typedef Object Filter(Object value);
-
-abstract class Transformer<T, V> {
-
-  T forward(V v);
-  V reverse(T t);
-  Transformer<V, T> get inverse => new _InverseTransformer/*<V, T>*/(this);
-}
-
-// TODO(jmesserly): restore types when Issue 14094 is fixed.
-class _InverseTransformer/*<V, T>*/ implements Transformer/*<V, T>*/ {
-  final Transformer/*<T, V>*/ _t;
-  _InverseTransformer(this._t);
-
-  /*V*/ forward(/*T*/ v) => _t.reverse(v);
-  /*T*/ reverse(/*V*/ t) => _t.forward(t);
-  Transformer/*<T, V>*/ get inverse => _t;
-}