This CL replaces std::string user_id in ash/* with AccountId.

chrome/browser/chromeos/file_system_provider/notification_manager.cc

 // Copyright 2014 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/file_system_provider/notification_manager.h"
 
 #include "base/strings/utf_string_conversions.h"
 #include "chrome/browser/browser_process.h"
 #include "chrome/browser/extensions/app_icon_loader_impl.h"
 #include "chrome/browser/ui/ash/multi_user/multi_user_util.h"
 #include "chrome/grit/generated_resources.h"
+#include "components/signin/core/account_id/account_id.h"
 #include "ui/base/l10n/l10n_util.h"
 #include "ui/message_center/message_center.h"
 #include "ui/message_center/notification.h"
 #include "ui/message_center/notification_delegate.h"
 #include "ui/message_center/notification_types.h"
 #include "ui/message_center/notifier_settings.h"
 
 namespace chromeos {
 namespace file_system_provider {
 namespace {
@@ skipping 89 matching lines @@
     icon_loader_->FetchImage(file_system_info_.extension_id());
 
   message_center::RichNotificationData rich_notification_data;
   rich_notification_data.buttons.push_back(
       message_center::ButtonInfo(l10n_util::GetStringUTF16(
           IDS_FILE_SYSTEM_PROVIDER_UNRESPONSIVE_ABORT_BUTTON)));
 
   message_center::NotifierId notifier_id(
       message_center::NotifierId::SYSTEM_COMPONENT,
       file_system_info_.mount_path().value());
-  notifier_id.profile_id = multi_user_util::GetUserIDFromProfile(profile_);
+  notifier_id.profile_id =
+      multi_user_util::GetAccountIdFromProfile(profile_).GetUserEmail();
 
   scoped_ptr<message_center::Notification> notification(
       new message_center::Notification(
           message_center::NOTIFICATION_TYPE_SIMPLE,
           file_system_info_.mount_path().value(),
           base::UTF8ToUTF16(file_system_info_.display_name()),
           l10n_util::GetStringUTF16(
               callbacks_.size() == 1
                   ? IDS_FILE_SYSTEM_PROVIDER_UNRESPONSIVE_WARNING
                   : IDS_FILE_SYSTEM_PROVIDER_MANY_UNRESPONSIVE_WARNING),
@@ skipping 11 matching lines @@
   while (it != callbacks_.end()) {
     CallbackMap::iterator current_it = it++;
     NotificationCallback callback = current_it->second;
     callbacks_.erase(current_it);
     callback.Run(result);
   }
 }
 
 }  // namespace file_system_provider
 }  // namespace chromeos