Experiment to understand test flakiness (#15872)

diff --git a/dev/devicelab/lib/tasks/plugin_tests.dart b/dev/devicelab/lib/tasks/plugin_tests.dart
index b9ee84f..3f032fa 100644
--- a/dev/devicelab/lib/tasks/plugin_tests.dart
+++ b/dev/devicelab/lib/tasks/plugin_tests.dart
@@ -97,6 +97,8 @@
         <String>['--stop'],
         canFail: true,
       );
+      // TODO(mravn): Investigating if flakiness is timing dependent.
+      await new Future<Null>.delayed(const Duration(seconds: 10));
     }
     await parent.delete(recursive: true);
   }