Fix warnings_checker.dart handling of multitests

tests/language_strong/mixin_super_constructor_positionals_test.dart

Index: tests/language_strong/mixin_super_constructor_positionals_test.dart
diff --git a/tests/language_strong/mixin_super_constructor_positionals_test.dart b/tests/language_strong/mixin_super_constructor_positionals_test.dart
index 78b44bb8980b6c4635c81521c379f03eef73daf1..6aad3c659c8ce7453efab330bf4c5f285fe463ff 100644
--- a/tests/language_strong/mixin_super_constructor_positionals_test.dart
+++ b/tests/language_strong/mixin_super_constructor_positionals_test.dart
@@ -7,9 +7,9 @@ import "package:expect/expect.dart";
 class Base {
   int i, j;
   Base.ctor(int this.i,
-            [ //                 /// 01: compile-time error
+            [ //                 //# 01: compile-time error
             int this.j
-            ] //                 /// 01: continued
+            ] //                 //# 01: continued
            );
 }
 
@@ -23,7 +23,7 @@ abstract class M {
 class C extends Base with M {
   int l = 131;
   C.foo() : super.ctor(1, 13);
-  C.bar() : super.ctor(1); //    /// 01: continued
+  C.bar() : super.ctor(1); //    //# 01: continued
 }
 
 main() {
@@ -33,5 +33,5 @@ main() {
   Expect.equals(14, c1.foo());
   Expect.equals(42, c1.k);
   Expect.equals(131, c1.l);
-  C c2 = new C.bar(); //         /// 01: continued
+  C c2 = new C.bar(); //         //# 01: continued
 }