Fix warnings_checker.dart handling of multitests

tests/language_strong/mixin_cyclic_test.dart

Index: tests/language_strong/mixin_cyclic_test.dart
diff --git a/tests/language_strong/mixin_cyclic_test.dart b/tests/language_strong/mixin_cyclic_test.dart
index 355a90300ebab6af262a9a024c23f21710e2aa02..ba23aab445688e4012b643598509bd6de888bac2 100644
--- a/tests/language_strong/mixin_cyclic_test.dart
+++ b/tests/language_strong/mixin_cyclic_test.dart
@@ -10,13 +10,13 @@ class S {}
 class M<T> {}
 
 class C1 = S with M;
-class C2 = S with C2; /// 01: compile-time error
+class C2 = S with C2; //# 01: compile-time error
 class C3 = S with M implements A;
-class C4 = S with M implements C4; /// 02: compile-time error
+class C4 = S with M implements C4; //# 02: compile-time error
 
 void main() {
   new C1();
-  new C2(); /// 01: continued
+  new C2(); //# 01: continued
   new C3();
-  new C4(); /// 02: continued
+  new C4(); //# 02: continued
 }