Fix warnings_checker.dart handling of multitests

tests/language/regress_27617_test.dart

Index: tests/language/regress_27617_test.dart
diff --git a/tests/language/regress_27617_test.dart b/tests/language/regress_27617_test.dart
index f584b44f9a2b08e72e8f995218d9e9332baa861b..c5f6c637b2773547088f32f2a5feda0e6d010ba5 100644
--- a/tests/language/regress_27617_test.dart
+++ b/tests/language/regress_27617_test.dart
@@ -8,9 +8,9 @@ class Foo {
   Foo._(this.greeting) { }
 
   // Const constructor must not redirect to non-const constructor.
-  const Foo.hi() : this._('hi'); // /// 1: compile-time error
+  const Foo.hi() : this._('hi'); // //# 1: compile-time error
 }
 
 main() {
-  const h = const Foo.hi(); // /// 1: continued
+  const h = const Foo.hi(); // //# 1: continued
 }