Fix warnings_checker.dart handling of multitests

tests/language_strong/class_cycle_test.dart

Index: tests/language_strong/class_cycle_test.dart
diff --git a/tests/language_strong/class_cycle_test.dart b/tests/language_strong/class_cycle_test.dart
index 18be64c3a957830f575ca2dad99015df1b87003a..8b58e2bb9e1239facea8c5592ed3a26bc393cd06 100644
--- a/tests/language_strong/class_cycle_test.dart
+++ b/tests/language_strong/class_cycle_test.dart
@@ -12,19 +12,19 @@ class C {
 }
 
 class Bar
-    extends Foo // /// 00: compile-time error
-    implements Foo // /// 01: compile-time error
+    extends Foo // //# 00: compile-time error
+    implements Foo // //# 01: compile-time error
 {
 }
 
 class ImplementsC implements C
-, C // /// 02: compile-time error
+, C // //# 02: compile-time error
 {}
 
 // Spec says: It is a compile-time error if the superclass
 // of a class C appears in the implements clause of C.
 class ExtendsC extends C
-implements C // /// 03: compile-time error
+implements C // //# 03: compile-time error
 {}
 
 main() {