Fix warnings_checker.dart handling of multitests

tests/language/callable_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.
 
 class X {
   call() => 42;
 }
 
 class Y {
   call(int x) => 87;
 }
 
 typedef F(int x);
 typedef G(String y);
 
 main() {
   X x = new X();
   Function f = x;  // Should pass checked mode test
   Y y = new Y();
   Function g = y;  // Should pass checked mode test
   F f0 = y;  // Should pass checked mode test
-  F f1 = x; // /// 00: dynamic type error, static type warning
-  G g0 = y; // /// 01: dynamic type error, static type warning
+  F f1 = x; // //# 00: dynamic type error, static type warning
+  G g0 = y; // //# 01: dynamic type error, static type warning
 }