cros: Clean up SessionStateDelegate refs in Chrome

components/user_manager/user_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 "components/user_manager/user_manager.h"
 
 #include "base/logging.h"
 #include "components/signin/core/account_id/account_id.h"
 
 namespace user_manager {
@@ skipping 74 matching lines @@
   return UserManager::instance;
 }
 
 // static
 UserManager* UserManager::SetForTesting(UserManager* user_manager) {
   UserManager* previous_instance = UserManager::instance;
   UserManager::instance = user_manager;
   return previous_instance;
 }
 
+ScopedUserSessionStateObserver::ScopedUserSessionStateObserver(
+    UserManager::UserSessionStateObserver* observer)
+    : observer_(observer) {
+  if (UserManager::IsInitialized())
+    UserManager::Get()->AddSessionStateObserver(observer_);
+}
+
+ScopedUserSessionStateObserver::~ScopedUserSessionStateObserver() {
+  if (UserManager::IsInitialized())
+    UserManager::Get()->RemoveSessionStateObserver(observer_);
+}
+
 }  // namespace user_manager