Replace ToLower calls to the new format

chromeos/cryptohome/system_salt_getter.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/cryptohome/system_salt_getter.h"
 
 #include "base/bind.h"
 #include "base/location.h"
 #include "base/single_thread_task_runner.h"
 #include "base/strings/string_number_conversions.h"
@@ skipping 77 matching lines @@
 // static
 SystemSaltGetter* SystemSaltGetter::Get() {
   CHECK(g_system_salt_getter)
       << "SystemSaltGetter::Get() called before Initialize()";
   return g_system_salt_getter;
 }
 
 // static
 std::string SystemSaltGetter::ConvertRawSaltToHexString(
     const std::vector<uint8>& salt) {
-  return base::StringToLowerASCII(base::HexEncode(
-      reinterpret_cast<const void*>(salt.data()), salt.size()));
+  return base::ToLowerASCII(
+      base::HexEncode(reinterpret_cast<const void*>(salt.data()), salt.size()));
 }
 
 }  // namespace chromeos