Mark periodic4-test as flaky and add debug information.

tests/lib/async/stream_periodic4_test.dart

Index: tests/lib/async/stream_periodic4_test.dart
diff --git a/tests/lib/async/stream_periodic4_test.dart b/tests/lib/async/stream_periodic4_test.dart
index 779947bf4264461e950cc4b4ee571f3d5c8bf451..5b6eda314416fb67bd139387bdf7f88552c5cf66 100644
--- a/tests/lib/async/stream_periodic4_test.dart
+++ b/tests/lib/async/stream_periodic4_test.dart
@@ -8,7 +8,13 @@ library dart.test.stream_from_iterable;
 import "dart:async";
 import '../../../pkg/unittest/lib/unittest.dart';
 
+int iteration = 0;
+
 void runTest(period, maxElapsed, pauseDuration) {
+  print("Iteration: $iteration");
+  var myIteration = iteration;
+  iteration++;
+
   Function done = expectAsync0(() { });
 
   Stopwatch watch = new Stopwatch()..start();
@@ -23,8 +29,10 @@ void runTest(period, maxElapsed, pauseDuration) {
         expect(true, false);
       } else {
         subscription.cancel();
+        print("Cancelling subscription of iteration: $myIteration");
         // Call 'done' ourself, since it won't be invoked in the onDone handler.
         runTest(period * 2, maxElapsed * 2, pauseDuration * 2);
+        print("Invoking done of iteration inside listener: $myIteration");
         done();
         return;
       }
@@ -38,7 +46,10 @@ void runTest(period, maxElapsed, pauseDuration) {
         subscription.resume();
       });
     }
-  }, onDone: done);
+  }, onDone: () {
+    print("Invoking done of iteration: $myIteration");
+    done();
+  });
 }
 
 main() {