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

chrome/browser/chromeos/settings/device_settings_provider.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 "chrome/browser/chromeos/settings/device_settings_provider.h"
 
 #include "base/bind.h"
 #include "base/bind_helpers.h"
 #include "base/callback.h"
 #include "base/command_line.h"
@@ skipping 64 matching lines @@
   kSignedDataRoamingEnabled,
   kStartUpFlags,
   kStartUpUrls,
   kStatsReportingPref,
   kSystemTimezonePolicy,
   kSystemUse24HourClock,
   kUpdateDisabled,
   kVariationsRestrictParameter,
 };
 
-// Legacy policy file location. Used to detect migration from pre v12 ChromeOS.
-const char kLegacyPolicyFile[] = "/var/lib/whitelist/preferences";
-
 bool HasOldMetricsFile() {
   // TODO(pastarmovj): Remove this once migration is not needed anymore.
   // If the value is not set we should try to migrate legacy consent file.
   // Loading consent file state causes us to do blocking IO on UI thread.
   // Temporarily allow it until we fix http://crbug.com/62626
   base::ThreadRestrictions::ScopedAllowIO allow_io;
   return GoogleUpdateSettings::GetCollectStatsConsent();
 }
 
 void LogShillError(
@@ skipping 908 matching lines @@
 void DeviceSettingsProvider::AttemptMigration() {
   if (device_settings_service_->HasPrivateOwnerKey()) {
     PrefValueMap::const_iterator i;
     for (i = migration_values_.begin(); i != migration_values_.end(); ++i)
       DoSet(i->first, *i->second);
     migration_values_.Clear();
   }
 }
 
 }  // namespace chromeos