shill: vpn: Implement NSS database interface class.

Use the NSS class to lookup NSS certificates for OpenVPN.

BUG=chromium-os:28792
TEST=unit tests

Change-Id: I2e0c7924d664f375f5b01bc73506e2b91e6f8720
Reviewed-on: https://gerrit.chromium.org/gerrit/19457
Tested-by: Darin Petkov <petkov@chromium.org>
Reviewed-by: Paul Stewart <pstew@chromium.org>
Commit-Ready: Darin Petkov <petkov@chromium.org>
diff --git a/mock_nss.cc b/mock_nss.cc
new file mode 100644
index 0000000..78d5603
--- /dev/null
+++ b/mock_nss.cc
@@ -0,0 +1,13 @@
+// Copyright (c) 2012 The Chromium OS 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 "shill/mock_nss.h"
+
+namespace shill {
+
+MockNSS::MockNSS() {}
+
+MockNSS::~MockNSS() {}
+
+}  // namespace shill