Roll Observatory packages and add a roll script

packages/initialize/lib/src/init_method.dart

 // Copyright (c) 2015, 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.
 part of initialize;
 
 /// Metadata used to label static or top-level methods that are called
 /// automatically when calling static_init.run(). This class is private because
 /// it shouldn't be used directly in annotations, instead use the `initMethod`
 /// singleton below.
 typedef dynamic _ZeroArg();
 class _InitMethod implements Initializer<_ZeroArg> {
   const _InitMethod();
 
   @override
   initialize(_ZeroArg method) => method();
 }
 
 /// We only ever need one instance of the `_InitMethod` class, this is it.
 const initMethod = const _InitMethod();