Add additional Schedule heartbeat calls.

pkg/scheduled_test/lib/scheduled_process.dart

Index: pkg/scheduled_test/lib/scheduled_process.dart
diff --git a/pkg/scheduled_test/lib/scheduled_process.dart b/pkg/scheduled_test/lib/scheduled_process.dart
index ad6d4daa4fd8b194928788e1e530fe10d0c8eaee..23370f10942602b5ccc0e42e56dbce3c3d87c70e 100644
--- a/pkg/scheduled_test/lib/scheduled_process.dart
+++ b/pkg/scheduled_test/lib/scheduled_process.dart
@@ -188,6 +188,12 @@ class ScheduledProcess {
       Future<Stream<List<int>>> streamFuture) {
     return streamWithCanceller(futureStream(streamFuture)
         .handleError((e) => currentSchedule.signalError(e))
+        .map((chunk) {
+      // Whenever the process produces any sort of output, reset the schedule's
+      // timer.
+      currentSchedule.heartbeat();
+      return chunk;
+    })
         .transform(new StringDecoder(_encoding))
         .transform(new LineTransformer()));
   }