Fix warnings_checker.dart handling of multitests

tests/language/regress_28217_test.dart

Index: tests/language/regress_28217_test.dart
diff --git a/tests/language/regress_28217_test.dart b/tests/language/regress_28217_test.dart
index 3cc40089731e53909fa05c6e4356e7bd7a6b19c2..0e55515a6fc6c255085a400cafd62acbe068a9fd 100644
--- a/tests/language/regress_28217_test.dart
+++ b/tests/language/regress_28217_test.dart
@@ -6,9 +6,9 @@
 // redirecting to a factory constructor.
 
 class B {
-  B() : this.a(); //   /// none: compile-time error
-  factory B.a() { } // /// 01: compile-time error
-  B.a(); //            /// 02: ok
+  B() : this.a(); //   //# none: compile-time error
+  factory B.a() { } // //# 01: compile-time error
+  B.a(); //            //# 02: ok
 }
 
 main() => new B();