Roll Observatory packages and add a roll script

packages/quiver/test/async/countdown_timer_test.dart

+// Copyright 2013 Google Inc. All Rights Reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+library quiver.async.countdown_timer_test;
+
+import 'package:test/test.dart';
+import 'package:quiver/async.dart';
+import 'package:quiver/time.dart';
+import 'package:quiver/testing/async.dart';
+import 'package:quiver/testing/time.dart';
+
+main() {
+  group('CountdownTimer', () {
+    test('should countdown', () {
+      new FakeAsync().run((FakeAsync async) {
+        var clock = async.getClock(new DateTime.fromMillisecondsSinceEpoch(0));
+        var stopwatch = new FakeStopwatch(
+            () => 1000 * clock.now().millisecondsSinceEpoch, 1000000);
+
+        var timings = new CountdownTimer(
+            new Duration(milliseconds: 500), new Duration(milliseconds: 100),
+            stopwatch: stopwatch).map((c) => c.remaining.inMilliseconds);
+
+        List<int> result;
+        timings.toList().then((list) {
+          result = list;
+        });
+
+        async.elapse(aMillisecond * 500);
+        expect(result, [400, 300, 200, 100, 0]);
+      });
+    });
+  });
+}