Fix warnings_checker.dart handling of multitests

tests/language_strong/error_stacktrace_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.
 // Dart test program for testing throw statement
 
 import "package:expect/expect.dart";
 
 class MyException {
   const MyException(String message) : message_ = message;
   final String message_;
@@ skipping 67 matching lines @@
   static int func4() {
     var i = 0;
     try {
       i = 10;
       func5();
     } on MyException catch (e) {
       i = 300;
       try {
         // There should be no stackTrace in this normal exception object.
         // We should get a NoSuchMethodError.
-        var trace = e.stackTrace; /// static type warning
+        var trace = e.stackTrace; //# static type warning
       } on NoSuchMethodError catch (e) {
         Expect.isNotNull(e.stackTrace, "Error needs a stackTrace on throw");
       }
     }
     return i;
   }
   static List func5() {
     // Throw an Exception (any random object).
     throw new MyException("MyException in func5");
   }
 }
 
 class ErrorStackTraceTest {
   static testMain() {
     Expect.equals(100, Helper1.func1());
     Expect.equals(200, Helper2.func1());
     Expect.equals(300, Helper3.func1());
   }
 }
 
 main() {
   ErrorStackTraceTest.testMain();
 }