anchor.diff:  
   main() {
     const ms5 = const Duration(milliseconds: 5);
  -  const halfSec = const Duration(milliseconds: 500);
  +  const twoSecs = const Duration(seconds: 2);
   
     test("stream timeout", () {
       StreamController c = new StreamController();
  
positive.code:       }
      });
      sw.start();
    });
  
    test("errors prevent timeout", () {
      Stopwatch sw = new Stopwatch();
      StreamController c = new StreamController();
      Stream tos = c.stream.timeout(halfSec, onTimeout: (_) {
        int elapsed = sw.elapsedMilliseconds;
        if (elapsed > 250) {
          // This should not happen, but it does occasionally.
  
negative.code:   test("events prevent timeout", () {
      Stopwatch sw = new Stopwatch();
      StreamController c = new StreamController();
      Stream tos = c.stream.timeout(twoSecs, onTimeout: (_) {
        int elapsed = sw.elapsedMilliseconds;
        if (elapsed > 250) {
          // This should not happen, but it does occasionally.
  