Roll Observatory packages and add a roll script

intl/lib/src/intl_helpers.dart

-// Copyright (c) 2012, 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.
-
-/**
- * A library for general helper code associated with the intl library
- * rather than confined to specific parts of it.
- */
-
-library intl_helpers;
-
-import 'dart:async';
-
-/**
- * This is used as a marker for a locale data map that hasn't been initialized,
- * and will throw an exception on any usage that isn't the fallback
- * patterns/symbols provided.
- */
-class UninitializedLocaleData<F> {
-  final String message;
-  final F fallbackData;
-  const UninitializedLocaleData(this.message, this.fallbackData);
-
-  operator [](String key) =>
-      (key == 'en_US') ? fallbackData : _throwException();
-
-  String lookupMessage(String message_str, [final String desc = '',
-      final Map examples = const {}, String locale, String name,
-      List<String> args, String meaning]) => message_str;
-
-  List get keys => _throwException();
-
-  bool containsKey(String key) => (key == 'en_US') ? true : _throwException();
-
-  _throwException() {
-    throw new LocaleDataException("Locale data has not been initialized"
-        ", call $message.");
-  }
-}
-
-class LocaleDataException implements Exception {
-  final String message;
-  LocaleDataException(this.message);
-  toString() => "LocaleDataException: $message";
-}
-
-/**
- *  An abstract superclass for data readers to keep the type system happy.
- */
-abstract class LocaleDataReader {
-  Future read(String locale);
-}
-
-/**
- * The internal mechanism for looking up messages. We expect this to be set
- * by the implementing package so that we're not dependent on its
- * implementation.
- */
-var messageLookup =
-    const UninitializedLocaleData('initializeMessages(<locale>)', null);
-
-/**
- * Initialize the message lookup mechanism. This is for internal use only.
- * User applications should import `message_lookup_by_library.dart` and call
- * `initializeMessages`
- */
-void initializeInternalMessageLookup(Function lookupFunction) {
-  if (messageLookup is UninitializedLocaleData) {
-    messageLookup = lookupFunction();
-  }
-}