Revert "Add ticks counter to Timer."

tests/lib_2/async/periodic_timer4_test.dart

-// Copyright (c) 2011, 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 timer_test;
-
-import 'dart:async';
-import 'package:expect/expect.dart';
-import 'package:async_helper/async_helper.dart';
-
-const ms = const Duration(milliseconds: 1);
-
-expectGTE(min, actual, msg) {
-  if (actual >= min) return;
-  Expect._fail(msg.replaceAll('{0}', "$min").replaceAll('{1}', "$actual"));
-}
-
-main() {
-  int interval = 20;
-  asyncStart();
-  var sw = new Stopwatch()..start();
-  int nextTick = 1;
-  bool running = true;
-  var timer = new Timer.periodic(ms * interval, (t) {
-    expectGTE(nextTick, t.tick, "tick {1} before expect next tick {0}.");
-    nextTick += 1;
-    int time = sw.elapsedMilliseconds;
-    int minTime = interval * t.tick;
-    expectGTE(minTime, time, "Actual time {1} before {0} at tick ${t.tick}");
-    if (t.tick > 20) {
-      running = false;
-      t.cancel();
-      asyncEnd();
-    }
-  });
-
-  /// Test that ticks still happen when the rest of the system is slow.
-  delay() {
-    int time = new DateTime.now().millisecondsSinceEpoch;
-    int limit = time + 3 * interval;
-    while (new DateTime.now().millisecondsSinceEpoch < limit) {
-      // Idle.
-    }
-    nextTick = timer.tick + 2; // At least increment by two, probably more.
-    if (running) Timer.run(delay);
-  }
-
-  Timer.run(delay);
-}