Make stream_timeout_test less likely to flake.

tests/lib/async/stream_timeout_test.dart

 // Copyright (c) 2013, 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.
 
 import "dart:async";
 import "package:unittest/unittest.dart";
 
 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();
     Stream tos = c.stream.timeout(ms5);
     expect(tos.isBroadcast, false);
     tos.handleError(expectAsync2((e, s) {
       expect(e, new isInstanceOf<TimeoutException>());
       expect(s, null);
     })).listen((v){ fail("Unexpected event"); });
   });
 
   test("stream timeout add events", () {
     StreamController c = new StreamController();
     Stream tos = c.stream.timeout(ms5, onTimeout: (sink) {
       sink.add(42);
       sink.addError("ERROR");
       sink.close();
     });
     expect(tos.isBroadcast, false);
     tos.listen(expectAsync1((v) { expect(v, 42); }),
                onError: expectAsync2((e, s) { expect(e, "ERROR"); }),
                onDone: expectAsync0((){}));
   });
 
   test("stream no timeout", () {
     StreamController c = new StreamController();
-    Stream tos = c.stream.timeout(halfSec);
+    Stream tos = c.stream.timeout(twoSecs);
     int ctr = 0;
     tos.listen((v) {
                  expect(v, 42);
                  ctr++;
                },
                onError: (e, s) { fail("No error expected"); },
                onDone: expectAsync0(() {
                  expect(ctr, 2);
                }));
     expect(tos.isBroadcast, false);
     c..add(42)..add(42)..close();  // Faster than a timeout!
   });
 
   test("stream timeout after events", () {
     StreamController c = new StreamController();
-    Stream tos = c.stream.timeout(halfSec);
+    Stream tos = c.stream.timeout(twoSecs);
     expect(tos.isBroadcast, false);
     int ctr = 0;
     tos.listen((v) {
                  expect(v, 42);
                  ctr++;
                },
                onError: expectAsync2((e, s) {
                  expect(ctr, 2);
                  expect(e, new isInstanceOf<TimeoutException>());
                }));
@@ skipping 26 matching lines @@
     expect(tos.isBroadcast, false);
     tos.handleError(expectAsync2((e, s) {
       expect(e, new isInstanceOf<TimeoutException>());
       expect(s, null);
     })).listen((v){ fail("Unexpected event"); });
   });
 
   test("events prevent timeout", () {
     Stopwatch sw = new Stopwatch();
     StreamController c = new StreamController();
-    Stream tos = c.stream.timeout(halfSec, onTimeout: (_) {
+    Stream tos = c.stream.timeout(twoSecs, onTimeout: (_) {
       int elapsed = sw.elapsedMilliseconds;
       if (elapsed > 250) {
         // This should not happen, but it does occasionally.
         // Starving the periodic timer has made the test useless.
         print("Periodic timer of 5 ms delayed $elapsed ms.");
         return;
       }
       fail("Timeout not prevented by events");
       throw "ERROR";
     });
-    tos.listen((v) { expect(v, 42);}, onDone: expectAsync0((){}));
+    // Start the periodic timer before we start listening to the stream.
+    // This should reduce the flakiness of the test.
     int ctr = 200;  // send this many events at 5ms intervals. Then close.
     new Timer.periodic(ms5, (timer) {
       sw.reset();
       c.add(42);
       if (--ctr == 0) {
         timer.cancel();
         c.close();
       }
     });
     sw.start();
+
+    tos.listen((v) { expect(v, 42);}, onDone: expectAsync0((){}));
   });
 
   test("errors prevent timeout", () {
     Stopwatch sw = new Stopwatch();
     StreamController c = new StreamController();
-    Stream tos = c.stream.timeout(halfSec, onTimeout: (_) {
+    Stream tos = c.stream.timeout(twoSecs, onTimeout: (_) {
       int elapsed = sw.elapsedMilliseconds;
       if (elapsed > 250) {
         // This should not happen, but it does occasionally.
         // Starving the periodic timer has made the test useless.
         print("Periodic timer of 5 ms delayed $elapsed ms.");
         return;
       }
       fail("Timeout not prevented by errors");
     });
-    tos.listen((_) {},
-      onError: (e, s) {
-        expect(e, "ERROR");
-      },
-      onDone: expectAsync0((){}));
+
+    // Start the periodic timer before we start listening to the stream.
+    // This should reduce the flakiness of the test.
     int ctr = 200;  // send this many error events at 5ms intervals. Then close.
     new Timer.periodic(ms5, (timer) {
       sw.reset();
       c.addError("ERROR");
       if (--ctr == 0) {
         timer.cancel();
         c.close();
       }
     });
     sw.start();
+
+    tos.listen((_) {},
+      onError: (e, s) {
+        expect(e, "ERROR");
+      },
+      onDone: expectAsync0((){}));
   });
 
   test("closing prevents timeout", () {
     StreamController c = new StreamController();
-    Stream tos = c.stream.timeout(halfSec, onTimeout: (_) {
+    Stream tos = c.stream.timeout(twoSecs, onTimeout: (_) {
       fail("Timeout not prevented by close");
     });
     tos.listen((_) {}, onDone: expectAsync0((){}));
     c.close();
   });
 
   test("pausing prevents timeout", () {
     StreamController c = new StreamController();
     Stream tos = c.stream.timeout(ms5, onTimeout: (_) {
       fail("Timeout not prevented by close");
     });
     var subscription = tos.listen((_) {}, onDone: expectAsync0((){}));
     subscription.pause();
-    new Timer(halfSec, () {
+    new Timer(twoSecs, () {
       c.close();
       subscription.resume();
     });
   });
 }