Fix warnings_checker.dart handling of multitests

tests/language/method_override2_test.dart

 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 // Checks that an overriding method has compatible parameters.
 
 abstract class I {
   m({a, b});
 }
 
 abstract class J extends I { }
 
 abstract class K extends J {
-  m({c, d}); // /// 00: static type warning
+  m({c, d}); // //# 00: static type warning
 }
 
 class C implements I {
   m({a, b}) {
     print("$a $b");
   }
 }
 
 class D
-    extends C // /// 01: static type warning
-    implements I // /// 02: static type warning
-    implements J // /// 03: static type warning
+    extends C // //# 01: static type warning
+    implements I // //# 02: static type warning
+    implements J // //# 03: static type warning
 {
   m({c, d}) {
     print("$c $d");
   }
 }
 
 
 int main() {
   var c = new C();
   c.m(a: "hello", b: "world");
   var d = new D();
   d.m(c: "hello", d: "world");
   print("${c is I} ${d is I} ${d is I} ${d is J}");
 }