user_manager component: Add UserManagerBase class.

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 "base/memory/scoped_ptr.h"
 #include "components/session_manager/session_manager_export.h"
 
@@ skipping 27 matching lines @@
   // Same as SESSION_STATE_LOGIN_PRIMARY but for multi-profiles sign in i.e.
   // when there's at least one user already active in the session.
   SESSION_STATE_LOGIN_SECONDARY,
 };
 
 class SESSION_EXPORT SessionManager {
  public:
   SessionManager();
   virtual ~SessionManager();
 
+  // Returns current SessionManager instance and NULL if it hasn't been
+  // initialized yet.
+  static SessionManager* Get();
+
   SessionState session_state() const { return session_state_; }
   virtual void SetSessionState(SessionState state);
 
   // Let session delegate executed on its plan of actions depending on the
   // current session type / state.
   void Start();
 
+  // Returns true when the browser has crashed and restarted during the current
+  // user's session.
+  static bool HasBrowserRestarted();
+
  protected:
   // Initializes SessionManager with delegate.
   void Initialize(SessionManagerDelegate* delegate);
 
+  // Sets SessionManager instance.
+  static void SetInstance(SessionManager* session_manager);
+
  private:
+  // Pointer to the existing SessionManager instance (if any).
+  // Set in ctor, reset in dtor. Not owned since specific implementation of
+  // SessionManager should decide on its own appropriate owner of SessionManager
+  // instance. For src/chrome implementation such place is
+  // g_browser_process->platform_part().
+  static SessionManager* instance;
+
   SessionState session_state_;
   scoped_ptr<SessionManagerDelegate> delegate_;
 
   DISALLOW_COPY_AND_ASSIGN(SessionManager);
 };
 
 class SESSION_EXPORT SessionManagerDelegate {
  public:
   SessionManagerDelegate();
   virtual ~SessionManagerDelegate();
 
   virtual void SetSessionManager(
       session_manager::SessionManager* session_manager);
 
   // Executes specific actions defined by this delegate.
   virtual void Start() = 0;
 
  protected:
   session_manager::SessionManager* session_manager_;
 
  private:
   DISALLOW_COPY_AND_ASSIGN(SessionManagerDelegate);
 };
 
 }  // namespace session_manager
 
 #endif  // COMPONENTS_SESSION_MANAGER_CORE_SESSION_MANAGER_H_