Fix warnings_checker.dart handling of multitests

tests/language/cyclic_class_member_test.dart

Index: tests/language/cyclic_class_member_test.dart
diff --git a/tests/language/cyclic_class_member_test.dart b/tests/language/cyclic_class_member_test.dart
index 63c9651c90ccc8b3bf1271832fffb91836c68e8f..d33d8966b56e5b6f5fbf6536085357dfeba3171f 100644
--- a/tests/language/cyclic_class_member_test.dart
+++ b/tests/language/cyclic_class_member_test.dart
@@ -5,7 +5,7 @@
 // Test that class with a cyclic hierarchy doesn't cause a loop in dart2js.
 
 class A
-    extends A /// 01: compile-time error
+    extends A //# 01: compile-time error
 {
   // When checking that foo isn't overriding an instance method in the
   // superclass, dart2js might loop.