lingering step 2 of the test rename overhaul: make await tests also a directory

frog/tests/await/try_catch3_test.dart

Index: frog/tests/await/try_catch3_test.dart
diff --git a/frog/tests/await/try_catch3_test.dart b/frog/tests/await/try_catch3_test.dart
index 9a391b9e9218f1493fc00c5d6a3fbe3d40822770..5231b250a341a17689397071d346533ede2c4906 100644
--- a/frog/tests/await/try_catch3_test.dart
+++ b/frog/tests/await/try_catch3_test.dart
@@ -2,6 +2,11 @@
 // 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.
 
+// The next line is used to tell test.dart that this test is run by invoking
+// awaitc.dart and passing this file as an argument (e.g. frog
+// frog/await/awaitc.dart test.dart):
+// VMOptions=frog/await/awaitc.dart
+
 // Await within a try-catch block, the awaited future produces the error.
 
 #import("await_test_helper.dart");