catchErrors and waitForCompletion now based on runZonedExperimental.

tests/lib/async/run_zoned2_test.dart

Index: tests/lib/async/run_zoned2_test.dart
diff --git a/tests/lib/async/catch_errors_test.dart b/tests/lib/async/run_zoned2_test.dart
similarity index 61%
copy from tests/lib/async/catch_errors_test.dart
copy to tests/lib/async/run_zoned2_test.dart
index 08ed6f50b3421e4f45f0cdd33a2c5f1648f56ecc..39e28a09815226922a8b50fe4f464095edfa6c20 100644
--- a/tests/lib/async/catch_errors_test.dart
+++ b/tests/lib/async/run_zoned2_test.dart
@@ -10,14 +10,7 @@ main() {
   // We keep a ReceivePort open until all tests are done. This way the VM will
   // hang if the callbacks are not invoked and the test will time out.
   var port = new ReceivePort();
-  // Make sure `catchErrors` shuts down the error stream when the synchronous
-  // operation is done and there isn't any asynchronous pending callback.
-  catchErrors(() {
-    return 'allDone';
-  }).listen((x) {
-      Expect.fail("Unexpected callback");
-    },
-    onDone: () {
-      port.close();
-    });
+  // Ensure that `runZoned` is done when a synchronous call finishes.
+  runZonedExperimental(() => 499,
+                       onDone: port.close);
 }