Revert "Make Zone API strong mode clean."

tests/lib/mirrors/invocation_fuzz_test.dart

Index: tests/lib/mirrors/invocation_fuzz_test.dart
diff --git a/tests/lib/mirrors/invocation_fuzz_test.dart b/tests/lib/mirrors/invocation_fuzz_test.dart
index 21a04fb71c0065042d867d0b6e6add7c71978257..d877c5a1d24ebece9aac730f9ed78c11a31d5f4c 100644
--- a/tests/lib/mirrors/invocation_fuzz_test.dart
+++ b/tests/lib/mirrors/invocation_fuzz_test.dart
@@ -207,8 +207,8 @@ main() {
   ];
   valueObjects.forEach((v) => checkInstance(reflect(v), 'value object'));
 
-  void uncaughtErrorHandler(self, parent, zone, error, stack) {}
-
+  uncaughtErrorHandler(self, parent, zone, error, stack) {}
+  ;
   var zoneSpec =
       new ZoneSpecification(handleUncaughtError: uncaughtErrorHandler);
   testZone = Zone.current.fork(specification: zoneSpec);