Add policy for limiting the session length

chrome/browser/chromeos/power/session_length_limiter.h

+// Copyright (c) 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_BROWSER_CHROMEOS_POWER_SESSION_LENGTH_LIMITER_H_
+#define CHROME_BROWSER_CHROMEOS_POWER_SESSION_LENGTH_LIMITER_H_
+
+#include "base/basictypes.h"
+#include "base/memory/scoped_ptr.h"
+#include "base/prefs/public/pref_change_registrar.h"
+#include "base/threading/thread_checker.h"
+#include "base/time.h"
+#include "base/timer.h"
+
+class PrefService;
+
+namespace chromeos {
+
+// Enforces a session length limit by terminating the session when the limit is
+// reached.
+class SessionLengthLimiter {
+ public:
+  class Delegate {
+   public:
+    virtual ~Delegate();
+
+    virtual const base::Time GetCurrentTime() const = 0;
+    virtual void StopSession() = 0;
+  };
+
+  // Registers preferences.
+  static void RegisterPrefs(PrefService* local_state);
+
+  SessionLengthLimiter(Delegate* delegate, bool browser_restarted);
+
+ private:
+  void OnSessionLengthLimitChanged();
+
+  // Starts a timer that periodically checks whether the remaining time has
+  // reached zero.
+  void StartTimer();
+
+  // Stops the timer.
+  void StopTimer();
+
+  // Updates the remaining time, and terminates the session when the time
+  // reaches zero.
+  void UpdateRemainingTime();
+
+  base::ThreadChecker thread_checker_;
+
+  scoped_ptr<Delegate> delegate_;
+  PrefChangeRegistrar pref_change_registrar_;
+
+  scoped_ptr<base::RepeatingTimer<SessionLengthLimiter> > repeating_timer_;
+  base::Time session_start_time_;
+  base::TimeDelta session_length_limit_;
+
+  DISALLOW_COPY_AND_ASSIGN(SessionLengthLimiter);
+};
+
+}  // namespace chromeos
+
+#endif  // CHROME_BROWSER_CHROMEOS_POWER_SESSION_LENGTH_LIMITER_H_