Fix warnings_checker.dart handling of multitests

tests/language/type_promotion_assign_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 type promotion of assigned locals.
 
 class A {
   var a = "a";
 }
 class B extends A {
   var b = "b";
 }
 class C extends B {
   var c = "c";
 }
 class D extends A {
   var d = "d";
 }
 class E implements C, D {
   var a = "";
   var b = "";
   var c = "";
   var d = "";
 }
 
 void main() {
   A a = new E();
   if (a is B) {
     print(a.a);
-    print(a.b); /// 01: static type warning
+    print(a.b); //# 01: static type warning
     a = null;
   }
   if (a is B) {
     a = null;
     print(a.a);
-    print(a.b); /// 02: static type warning
+    print(a.b); //# 02: static type warning
   }
   if (a is B) {
     print(a.a);
-    print(a.b); /// 03: static type warning
+    print(a.b); //# 03: static type warning
     {
       a = null;
     }
     print(a.a);
-    print(a.b); /// 04: static type warning
+    print(a.b); //# 04: static type warning
   }
 }