Roll Observatory packages and add a roll script

quiver/lib/src/async/countdown_timer.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.
-
-part of quiver.async;
-
-/**
- * A simple countdown timer that fires events in regular increments until a
- * duration has passed.
- *
- * CountdownTimer implements [Stream] and sends itself as the event. From the
- * timer you can get the [remaining] and [elapsed] time, or [cancel] the timer.
- */
-class CountdownTimer extends Stream<CountdownTimer> {
-  static const _THRESHOLD_MS = 4;
-
-  final Duration _duration;
-  final Duration _increment;
-  final Stopwatch _stopwatch;
-  final StreamController<CountdownTimer> _controller;
-  Timer _timer;
-
-  /**
-   * Creates a new [CountdownTimer] that fires events in increments of
-   * [increment], until the [duration] has passed.
-   *
-   * [stopwatch] is for testing purposes. If you're using CountdownTimer and
-   * need to control time in a test, pass a mock or a fake. See [FakeAsync] and
-   * [FakeStopwatch].
-   */
-  CountdownTimer(Duration duration, Duration increment, {Stopwatch stopwatch})
-      : _duration = duration,
-        _increment = increment,
-        _stopwatch = stopwatch == null ? new Stopwatch() : stopwatch,
-        _controller = new StreamController<CountdownTimer>.broadcast(
-            sync: true) {
-    _timer = new Timer.periodic(increment, _tick);
-    _stopwatch.start();
-  }
-
-  StreamSubscription<CountdownTimer> listen(void onData(CountdownTimer event),
-          {Function onError, void onDone(), bool cancelOnError}) =>
-      _controller.stream.listen(onData, onError: onError, onDone: onDone);
-
-  Duration get elapsed => _stopwatch.elapsed;
-
-  Duration get remaining => _duration - _stopwatch.elapsed;
-
-  bool get isRunning => _stopwatch.isRunning;
-
-  cancel() {
-    _stopwatch.stop();
-    _timer.cancel();
-    _controller.close();
-  }
-
-  _tick(Timer timer) {
-    var t = remaining;
-    _controller.add(this);
-    // timers may have a 4ms resolution
-    if (t.inMilliseconds < _THRESHOLD_MS) {
-      cancel();
-    }
-  }
-}