Implemented system tray UI for new account management.

ash/system/user/user_accounts_delegate.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 "ash/system/user/user_accounts_delegate.h"
+
+namespace ash {
+namespace tray {
+
+UserAccountsDelegate::UserAccountsDelegate() {}
+
+UserAccountsDelegate::~UserAccountsDelegate() {}
+
+void UserAccountsDelegate::AddObserver(Observer* observer) {
+  observers_.AddObserver(observer);
+}
+
+void UserAccountsDelegate::RemoveObserver(Observer* observer) {
+  observers_.RemoveObserver(observer);
+}
+
+void UserAccountsDelegate::NotifyAccountListChanged() {
+  FOR_EACH_OBSERVER(Observer, observers_, AccountListChanged());
+}
+
+}  // namespace tray
+}  // namespace ash