Fix warnings_checker.dart handling of multitests

tests/language/generic_field_mixin6_test.dart

 // Copyright (c) 2014, 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.
 
 // Test that generic types in mixins are handled.
 
 import 'package:expect/expect.dart';
 
 class M<T> {
-  T field = 0; /// 01: static type warning
+  T field = 0; //# 01: static type warning
 }
 class A<U> {}
 class C1<V> = Object with M<V>;
 class C2 = Object with M<int>;
 class C3 = Object with M<String>;
 
 main() {
-  checkNoDynamicTypeError(() => new C1<int>()); // /// 01: continued
-  checkDynamicTypeError(() => new C1<String>()); /// 01: continued
+  checkNoDynamicTypeError(() => new C1<int>()); // //# 01: continued
+  checkDynamicTypeError(() => new C1<String>()); //# 01: continued
 
-  checkNoDynamicTypeError(() => new C2()); //      /// 01: continued
+  checkNoDynamicTypeError(() => new C2()); //      //# 01: continued
 
-  checkDynamicTypeError(() => new C3()); //        /// 01: continued
+  checkDynamicTypeError(() => new C3()); //        //# 01: continued
 }
 
 /// Returns `true` if the program is running in checked mode.
 bool inCheckedMode() {
   try {
     var i = 42;
     String s = i;
   } on TypeError catch (e) {
     return true;
   }
@@ skipping 18 matching lines @@
 /// of execution mode.
 void checkNoDynamicTypeError(f(), [String message]) {
   message = message != null ? ': $message' : '';
   try {
     f();
   } on TypeError catch (e) {
     String mode = inCheckedMode() ? 'checked mode' : 'production mode';
     Expect.fail('Unexpected type error in $mode$message.');
   }
 }