fix checked-mode running of isolaterunner_test

R=lrn@google.com

Review URL: https://codereview.chromium.org//1028193003
diff --git a/test/isolaterunner_test.dart b/test/isolaterunner_test.dart
index 4b98b58..9b0b3b6 100644
--- a/test/isolaterunner_test.dart
+++ b/test/isolaterunner_test.dart
@@ -111,4 +111,4 @@
 
 var _global;
 getGlobal(_) => _global;
-void setGlobal(v) => _global = v;
+setGlobal(v) => _global = v;