session_manager: Add SessionManagerObserver interface

components/session_manager/core/session_manager.h

 // 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.
 
 #ifndef COMPONENTS_SESSION_MANAGER_CORE_SESSION_MANAGER_H_
 #define COMPONENTS_SESSION_MANAGER_CORE_SESSION_MANAGER_H_
 
 #include <vector>
 
 #include "base/macros.h"
+#include "base/observer_list.h"
 #include "components/session_manager/session_manager_export.h"
 #include "components/session_manager/session_manager_types.h"
 
 class AccountId;
 
 namespace session_manager {
 
+class SessionManagerObserver;
+
 class SESSION_EXPORT SessionManager {
  public:
   SessionManager();
   virtual ~SessionManager();
 
   // Returns current SessionManager instance and NULL if it hasn't been
   // initialized yet.
   static SessionManager* Get();
 
   void SetSessionState(SessionState state);
@@ skipping 11 matching lines @@
   virtual bool IsSessionStarted() const;
 
   // Called when browser session is started i.e. after
   // browser_creator.LaunchBrowser(...) was called after user sign in.
   // When user is at the image screen IsUserLoggedIn() will return true
   // but IsSessionStarted() will return false. During the kiosk splash screen,
   // we perform additional initialization after the user is logged in but
   // before the session has been started.
   virtual void SessionStarted();
 
+  void AddObserver(SessionManagerObserver* observer);
+  void RemoveObserver(SessionManagerObserver* observer);
+
   SessionState session_state() const { return session_state_; }
   const std::vector<Session>& sessions() const { return sessions_; }
 
  protected:
   // Notifies UserManager about a user signs in when creating a user session.
   virtual void NotifyUserLoggedIn(const AccountId& user_account_id,
                                   const std::string& user_id_hash,
                                   bool browser_restart);
 
   // Sets SessionManager instance.
@@ skipping 18 matching lines @@
 
   // Id of the primary session, i.e. the first user session.
   static const SessionId kPrimarySessionId = 1;
 
   // ID assigned to the next session.
   SessionId next_id_ = kPrimarySessionId;
 
   // Keeps track of user sessions.
   std::vector<Session> sessions_;
 
+  base::ObserverList<SessionManagerObserver> observers_;
+
   DISALLOW_COPY_AND_ASSIGN(SessionManager);
 };
 
 }  // namespace session_manager
 
 #endif  // COMPONENTS_SESSION_MANAGER_CORE_SESSION_MANAGER_H_