Add SessionStateObserver with ActiveUserChanged()

chrome/common/chrome_notification_types.h

 // Copyright 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.
 
 #ifndef CHROME_COMMON_CHROME_NOTIFICATION_TYPES_H_
 #define CHROME_COMMON_CHROME_NOTIFICATION_TYPES_H_
 
 #include "build/build_config.h"
 #include "content/public/browser/notification_types.h"
 
@@ skipping 872 matching lines @@
   // Sent when PerformanceMonitor has finished all the initial steps of data
   // collection and has begun passively observing. The source is the
   // PerformanceMonitor*. No details are expected.
   NOTIFICATION_PERFORMANCE_MONITOR_INITIALIZED,
 
 #if defined(OS_CHROMEOS)
   // Sent when a chromium os user logs in.
   // The details are a chromeos::User object.
   NOTIFICATION_LOGIN_USER_CHANGED,
 
-  // Sent when a chromium os active user has changed.
-  // The details are a chromeos::User object.
-  // This notification is _not_ sent when user logs in to a new or existing
-  // session because NOTIFICATION_LOGIN_USER_CHANGED is sent instead.
-  NOTIFICATION_ACTIVE_USER_CHANGED,
-
   // Sent immediately after the logged-in user's profile is ready.
   // The details are a Profile object.
   NOTIFICATION_LOGIN_USER_PROFILE_PREPARED,
 
   // Sent when the chromium session of a particular user is started.
   // If this is a new user on the machine this will not be sent until a profile
   // picture has been selected, unlike NOTIFICATION_LOGIN_USER_CHANGED which is
   // sent immediately after the user has logged in. This will be sent again if
   // the browser crashes and restarts.
   // The details are a chromeos::User object.
@@ skipping 336 matching lines @@
   // Note:-
   // Currently only Content and Chrome define and use notifications.
   // Custom notifications not belonging to Content and Chrome should start
   // from here.
   NOTIFICATION_CHROME_END,
 };
 
 }  // namespace chrome
 
 #endif  // CHROME_COMMON_CHROME_NOTIFICATION_TYPES_H_