Use a direct include of strings headers in chromeos/.

chromeos/network/onc/onc_certificate_importer_unittest.cc

 // Copyright (c) 2012 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 "chromeos/network/onc/onc_certificate_importer.h"
 
 #include <cert.h>
 #include <certdb.h>
 #include <keyhi.h>
 #include <pk11pub.h>
 #include <string>
 
 #include "base/logging.h"
-#include "base/string_number_conversions.h"
+#include "base/strings/string_number_conversions.h"
 #include "base/values.h"
 #include "chromeos/network/onc/onc_constants.h"
 #include "chromeos/network/onc/onc_test_utils.h"
 #include "crypto/nss_util.h"
 #include "net/base/crypto_module.h"
 #include "net/cert/cert_type.h"
 #include "net/cert/nss_cert_database.h"
 #include "net/cert/x509_certificate.h"
 #include "testing/gtest/include/gtest/gtest.h"
 
@@ skipping 281 matching lines @@
                   "certificate-client-update.onc"),
         CertParam(net::SERVER_CERT,
                   "certificate-server.onc",
                   "certificate-server-update.onc"),
         CertParam(net::CA_CERT,
                   "certificate-web-authority.onc",
                   "certificate-web-authority-update.onc")));
 
 }  // namespace onc
 }  // namespace chromeos