Fix warnings_checker.dart handling of multitests

tests/language/class_override_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.
 
 // It is a static warning if a method m1 overrides a method m2 and has a
 // different number of required parameters.
 
 class A {
   foo() {}
 }
 
 class B extends A {
-  foo(a) {} // /// 00: static type warning
+  foo(a) {} // //# 00: static type warning
 }
 
 main() {
   B instance = new B();
   try {
     instance.foo();
-  } on NoSuchMethodError catch (error) { // /// 00: continued
+  } on NoSuchMethodError catch (error) { // //# 00: continued
   } finally {
   }
   print("Success");
 }