settings: Add async system salt retrieval logic in DeviceOAuth2TokenServiceFactory

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/message_loop/message_loop_proxy.h"
 #include "base/strings/string_number_conversions.h"
@@ skipping 20 matching lines @@
       base::Bind(&SystemSaltGetter::GetSystemSaltInternal,
                  weak_ptr_factory_.GetWeakPtr(),
                  callback));
 }
 
 std::string SystemSaltGetter::GetSystemSaltSync() {
   LoadSystemSalt();  // no-op if it's already loaded.
   return system_salt_;
 }
 
-std::string SystemSaltGetter::GetCachedSystemSalt() {
-  return system_salt_;
-}
-
 void SystemSaltGetter::GetSystemSaltInternal(
     const GetSystemSaltCallback& callback,
     bool service_is_available) {
   LOG_IF(ERROR, !service_is_available) << "WaitForServiceToBeAvailable failed.";
   // TODO(hashimoto): Stop using GetSystemSaltSync(). crbug.com/141009
   callback.Run(GetSystemSaltSync());
 }
 
 void SystemSaltGetter::LoadSystemSalt() {
   if (!system_salt_.empty())
@@ skipping 33 matching lines @@
 }
 
 // static
 std::string SystemSaltGetter::ConvertRawSaltToHexString(
     const std::vector<uint8>& salt) {
   return StringToLowerASCII(base::HexEncode(
       reinterpret_cast<const void*>(salt.data()), salt.size()));
 }
 
 }  // namespace chromeos