Replace calls to rand_s with calls to RtlGenRandom

sandbox/win/src/sandbox_rand.cc

+// Copyright (c) 2015 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "sandbox/win/src/sandbox_rand.h"
+
+#include <windows.h>
+
+// #define needed to link in RtlGenRandom(), a.k.a. SystemFunction036.  See the
+// "Community Additions" comment on MSDN here:
+// http://msdn.microsoft.com/en-us/library/windows/desktop/aa387694.aspx
+#define SystemFunction036 NTAPI SystemFunction036
+#include <NTSecAPI.h>
+#undef SystemFunction036
+
+namespace sandbox {
+
+bool GetRandom(unsigned int* random_value) {
+  return RtlGenRandom(random_value, sizeof(unsigned int)) != FALSE;
+}
+
+}  // namespace sandbox