Fix warnings_checker.dart handling of multitests

tests/language_strong/proxy3_test.dart

 // Copyright (c) 2013, 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 for static warnings for member access on classes with @proxy annotation.
 
 const isFalse = identical(-0.0, 0);
 
 const validProxy = isFalse ? null : proxy;
 const invalidProxy = isFalse ? proxy : null;
 
 @validProxy
 class ValidProxy {}
 
 @invalidProxy
 class InvalidProxy {}
 
 main() {
-  try { new InvalidProxy().foo; } catch (e) {} // /// 01: static type warning
-  try { new InvalidProxy().foo(); } catch (e) {} // /// 02: static type warning
+  try { new InvalidProxy().foo; } catch (e) {} // //# 01: static type warning
+  try { new InvalidProxy().foo(); } catch (e) {} // //# 02: static type warning
 
-  try { new ValidProxy().foo; } catch (e) {} /// 03: ok
-  try { new ValidProxy().foo(); } catch (e) {} /// 04: ok
+  try { new ValidProxy().foo; } catch (e) {} //# 03: ok
+  try { new ValidProxy().foo(); } catch (e) {} //# 04: ok
 }