We should use UserID object to identify users instead of username.

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/logging.h"
@@ skipping 501 matching lines @@
       NotifyObservers(path);
       return;
     }
   } else {
     // Temporary store new setting in
     // |device_settings_|. |device_settings_| will be stored on a disk
     // as soon as an ownership of device the will be taken.
     OwnerSettingsServiceChromeOS::UpdateDeviceSettings(
         path, in_value, device_settings_);
     em::PolicyData data;
-    data.set_username(device_settings_service_->GetUsername());
+    data.set_username(device_settings_service_->GetUserID().GetUserEmail());
     CHECK(device_settings_.SerializeToString(data.mutable_policy_value()));
 
     // Set the cache to the updated value.
     UpdateValuesCache(data, device_settings_, TEMPORARILY_UNTRUSTED);
 
     if (!device_settings_cache::Store(data, g_browser_process->local_state())) {
       LOG(ERROR) << "Couldn't store to the temp storage.";
       NotifyObservers(path);
       return;
     }
@@ skipping 26 matching lines @@
     // Apply the locally-accumulated device settings on top of the initial
     // settings from the service and write back the result.
     if (device_settings_service_->device_settings()) {
       em::ChromeDeviceSettingsProto new_settings(
           *device_settings_service_->device_settings());
       new_settings.MergeFrom(device_settings_);
       device_settings_.Swap(&new_settings);
     }
 
     scoped_ptr<em::PolicyData> policy(new em::PolicyData());
-    policy->set_username(device_settings_service_->GetUsername());
+    policy->set_username(device_settings_service_->GetUserID().GetUserEmail());
     CHECK(device_settings_.SerializeToString(policy->mutable_policy_value()));
     if (!device_settings_service_->GetOwnerSettingsService()
              ->CommitTentativeDeviceSettings(policy.Pass())) {
       LOG(ERROR) << "Can't store policy";
     }
   }
 
   // The owner key might have become available, allowing migration to happen.
   AttemptMigration();
 
@@ skipping 239 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