Fix windows build.

runtime/bin/test_extension.c

 /* 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.
  */
 #include <assert.h>
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
 
 #include "include/dart_api.h"
@@ skipping 35 matching lines @@
   }
   if ((strcmp("TestExtension_ThrowMeTheBall", c_name) == 0) && (argc == 1)) {
     return ThrowMeTheBall;
   }
   return NULL;
 }
 
 
 /* Native entry point for the extension library. */
 DART_EXPORT Dart_Handle test_extension_Init(Dart_Handle parent_library) {
+  Dart_Handle result_code;
   if (Dart_IsError(parent_library)) {
     return parent_library;
   }
 
-  Dart_Handle result_code =
-      Dart_SetNativeResolver(parent_library, ResolveName);
+  result_code = Dart_SetNativeResolver(parent_library, ResolveName);
   if (Dart_IsError(result_code)) {
     return result_code;
   }
 
   return parent_library;
 }
-