Add safetymargin for timer tests in browsers.

tests/lib/async/multiple_timer_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 multiple_timer_test;
 
 import 'dart:async';
 import '../../../pkg/unittest/lib/unittest.dart';
 
 const Duration TIMEOUT1 = const Duration(seconds: 1);
 const Duration TIMEOUT2 = const Duration(seconds: 2);
 const Duration TIMEOUT3 = const Duration(milliseconds: 500);
 const Duration TIMEOUT4 = const Duration(milliseconds: 1500);
 
+// The stopwatch is more precise than the Timer. It can happen that
+// the TIMEOUT triggers *slightly* too early on the VM. So we add a millisecond
+// as safetymargin.
+// Some browsers (Firefox and IE so far) can trigger too early. So we add more
+// margin. We use identical(1, 1.0) as an easy way to know if the test is
+// compiled by dart2js.
+int get safetyMargin => identical(1, 1.0) ? 1 : 100;
+
 main() {
   test("multiple timer test", () {
     Stopwatch _stopwatch1 = new Stopwatch();
     Stopwatch _stopwatch2 = new Stopwatch();
     Stopwatch _stopwatch3 = new Stopwatch();
     Stopwatch _stopwatch4 = new Stopwatch();
     List<int> _order;
     int _message;
 
     void timeoutHandler1() {
-      // The stopwatch is more precise than the Timer. It can happen that
-      // the TIMEOUT triggers *slightly* too early.
-      expect(_stopwatch1.elapsedMilliseconds + 1,
+      expect(_stopwatch1.elapsedMilliseconds + safetyMargin,
              greaterThanOrEqualTo(TIMEOUT1.inMilliseconds));
       expect(_order[_message], 0);
       _message++;
     }
 
     void timeoutHandler2() {
-      // The stopwatch is more precise than the Timer. It can happen that
-      // the TIMEOUT triggers *slightly* too early.
-      expect(_stopwatch2.elapsedMilliseconds + 1,
+      expect(_stopwatch2.elapsedMilliseconds + safetyMargin,
              greaterThanOrEqualTo(TIMEOUT2.inMilliseconds));
       expect(_order[_message], 1);
       _message++;
     }
 
     void timeoutHandler3() {
-      // The stopwatch is more precise than the Timer. It can happen that
-      // the TIMEOUT triggers *slightly* too early.
-      expect(_stopwatch3.elapsedMilliseconds + 1,
+      expect(_stopwatch3.elapsedMilliseconds + safetyMargin,
              greaterThanOrEqualTo(TIMEOUT3.inMilliseconds));
       expect(_order[_message], 2);
       _message++;
     }
 
     void timeoutHandler4() {
-      // The stopwatch is more precise than the Timer. It can happen that
-      // the TIMEOUT triggers *slightly* too early.
-      expect(_stopwatch4.elapsedMilliseconds + 1,
+      expect(_stopwatch4.elapsedMilliseconds + safetyMargin,
              greaterThanOrEqualTo(TIMEOUT4.inMilliseconds));
       expect(_order[_message], 3);
       _message++;
     }
 
     _order = new List<int>(4);
     _order[0] = 2;
     _order[1] = 0;
     _order[2] = 3;
     _order[3] = 1;
     _message = 0;
 
     _stopwatch1.start();
     new Timer(TIMEOUT1, expectAsync0(timeoutHandler1));
     _stopwatch2.start();
     new Timer(TIMEOUT2, expectAsync0(timeoutHandler2));
     _stopwatch3.start();
     new Timer(TIMEOUT3, expectAsync0(timeoutHandler3));
     _stopwatch4.start();
     new Timer(TIMEOUT4, expectAsync0(timeoutHandler4));
   });
 }