Roll Observatory packages and add a roll script

packages/unittest/test/breath_test.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.
+
+library unittest.breath_test;
+
+import 'dart:async';
+
+import 'package:unittest/unittest.dart';
+
+void main() {
+  // Test the sync test 'breath' feature of unittest.
+
+  // We use the testStartStopwatch to determine if the 'starve'
+  // test was executed within a small enough time interval from
+  // the first test that we are guaranteed the second test is
+  // running in a microtask. If the second test is running as a
+  // microtask we are guaranteed the timer scheduled in the
+  // first test has not been run yet.
+  var testStartStopwatch = new Stopwatch()..start();
+
+  group('breath', () {
+    var sentinel = 0;
+
+    test('initial', () {
+      Timer.run(() {
+        sentinel = 1;
+      });
+    });
+
+    test('starve', () {
+      // If less than BREATH_INTERVAL time has passed since before
+      // we started the test group then the previous test's timer
+      // has not been run (at least this is what we are testing).
+      if (testStartStopwatch.elapsed.inMilliseconds <= BREATH_INTERVAL) {
+        expect(sentinel, 0);
+      }
+
+      // Next we wait for at least BREATH_INTERVAL to guaranteed the
+      // next (third) test is run using a timer which means it will
+      // run after the timer scheduled in the first test and hence
+      // the sentinel should have been set to 1.
+      var sw = new Stopwatch()..start();
+      while (sw.elapsed.inMilliseconds < BREATH_INTERVAL);
+    });
+
+    test('breathed', () {
+      expect(sentinel, 1);
+    });
+  });
+}