linux and chromeos: Turn on -Wunused-const-variable.

chrome/browser/chromeos/login/fake_supervised_user_manager.cc

 // Copyright 2013 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 "chrome/browser/chromeos/login/fake_supervised_user_manager.h"
 
 #include <string>
 
-namespace {
-
-// As defined in /chromeos/dbus/cryptohome_client.cc.
-static const char kUserIdHashSuffix[] = "-hash";
-
-}  // namespace
-
 namespace chromeos {
 
 FakeSupervisedUserManager::FakeSupervisedUserManager()  {}
 
 FakeSupervisedUserManager::~FakeSupervisedUserManager() {
 }
 
 const User* FakeSupervisedUserManager::CreateUserRecord(
     const std::string& manager_id,
     const std::string& local_user_id,
@@ skipping 30 matching lines @@
     const std::string& managed_user_id) const {
   return std::string();
 }
 
 std::string FakeSupervisedUserManager::GetManagerDisplayEmail(
     const std::string& managed_user_id) const {
   return std::string();
 }
 
 }  // namespace chromeos