Fix Win64 build of Dart VM.

runtime/bin/platform_win.cc

 // 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 "platform/globals.h"
 #if defined(TARGET_OS_WINDOWS)
 
 #include "bin/platform.h"
 #include "bin/log.h"
 #include "bin/socket.h"
@@ skipping 41 matching lines @@
   tmp = strings;
   for (intptr_t current = 0; current < i; current++) {
     result[current] = StringUtils::WideToUtf8(tmp);
     tmp += (wcslen(tmp) + 1);
   }
   FreeEnvironmentStringsW(strings);
   return result;
 }
 
 
-void Platform::FreeEnvironment(char** env, int count) {
-  for (int i = 0; i < count; i++) free(env[i]);
+void Platform::FreeEnvironment(char** env, intptr_t count) {
+  for (intptr_t i = 0; i < count; i++) {
+    free(env[i]);
+  }
   delete[] env;
 }
 
 }  // namespace bin
 }  // namespace dart
 
 #endif  // defined(TARGET_OS_WINDOWS)