Fix warnings_checker.dart handling of multitests

tests/language/unsupported_operators_test.dart

Index: tests/language/unsupported_operators_test.dart
diff --git a/tests/language/unsupported_operators_test.dart b/tests/language/unsupported_operators_test.dart
index a80987f11e231a234fe43dfff5cf8fd2a4f4e929..d5ba5ebae93c9637b06ae9c2a800a74d508dc669 100644
--- a/tests/language/unsupported_operators_test.dart
+++ b/tests/language/unsupported_operators_test.dart
@@ -9,10 +9,10 @@ library unsupported_operators;
 class C {
   m() {
     print(
-          super === /// 01: compile-time error
+          super === //# 01: compile-time error
           null);
     print(
-          super !== /// 02: compile-time error
+          super !== //# 02: compile-time error
           null);
   }
 }
@@ -21,9 +21,9 @@ void main() {
   new C().m();
   new C().m();
   print(
-        "foo" === /// 03: compile-time error
+        "foo" === //# 03: compile-time error
         null);
   print(
-        "foo" !== /// 04: compile-time error
+        "foo" !== //# 04: compile-time error
         null);
 }