Fix warnings_checker.dart handling of multitests

tests/language_strong/mixin_black_listed_test.dart

Index: tests/language_strong/mixin_black_listed_test.dart
diff --git a/tests/language_strong/mixin_black_listed_test.dart b/tests/language_strong/mixin_black_listed_test.dart
index c8a7c4894f3b592a63b5f2ead73f875537bafb3e..fc8eefec7bebe5879e6a5025d8c1970a4a704850 100644
--- a/tests/language_strong/mixin_black_listed_test.dart
+++ b/tests/language_strong/mixin_black_listed_test.dart
@@ -10,33 +10,33 @@ class C {}
 class D {}
 
 class C1 extends Object
-with String /// 01: compile-time error
+with String //# 01: compile-time error
 {}
 
 class D1 extends Object with C
-, Null /// 02: compile-time error
+, Null //# 02: compile-time error
 {}
 
 class E1 extends Object with
-int, /// 03: compile-time error
+int, //# 03: compile-time error
 C {}
 
 class F1 extends Object with C
-, double /// 04: compile-time error
+, double //# 04: compile-time error
 , D {}
 
-class C2 = Object with num; /// 05: compile-time error
+class C2 = Object with num; //# 05: compile-time error
 
 class D2 = Object with C
-, bool /// 06: compile-time error
+, bool //# 06: compile-time error
 ;
 
 class E2 = Object with
-String, /// 07: compile-time error
+String, //# 07: compile-time error
 C;
 
 class F2 = Object with C,
-dynamic, /// 08: compile-time error
+dynamic, //# 08: compile-time error
 D;
 
 
@@ -45,7 +45,7 @@ main() {
   Expect.isNotNull(new D1());
   Expect.isNotNull(new E1());
   Expect.isNotNull(new F1());
-  Expect.isNotNull(new C2()); /// 05: continued
+  Expect.isNotNull(new C2()); //# 05: continued
   Expect.isNotNull(new D2());
   Expect.isNotNull(new E2());
   Expect.isNotNull(new F2());