Add countdown when session time is limited

ash/system/tray/system_tray_delegate.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 ASH_SYSTEM_TRAY_SYSTEM_TRAY_DELEGATE_H_
 #define ASH_SYSTEM_TRAY_SYSTEM_TRAY_DELEGATE_H_
 
 #include <string>
 #include <vector>
 
 #include "ash/ash_export.h"
 #include "ash/system/power/power_supply_status.h"
 #include "ash/system/user/login_status.h"
 #include "base/file_path.h"
 #include "base/i18n/time_formatting.h"
 #include "base/memory/scoped_ptr.h"
 #include "base/string16.h"
+#include "base/time.h"
 #include "ui/gfx/image/image_skia.h"
 
 namespace ash {
 
 struct ASH_EXPORT NetworkIconInfo {
   NetworkIconInfo();
   ~NetworkIconInfo();
 
   bool connecting;
   bool connected;
@@ skipping 264 matching lines @@
   // Shows UI for changing proxy settings.
   virtual void ChangeProxySettings() = 0;
 
   // Returns VolumeControlDelegate.
   virtual VolumeControlDelegate* GetVolumeControlDelegate() const = 0;
 
   // Sets VolumeControlDelegate.
   virtual void SetVolumeControlDelegate(
       scoped_ptr<VolumeControlDelegate> delegate) = 0;
 
+  // Returns the session start time, or a zero base::Time if no session start
+  // time is set.
+  virtual base::Time GetSessionStartTime() = 0;
+
+  // Returns the session length limit, or a zero base::TimeDelta if no session
+  // length limit is set.
+  virtual base::TimeDelta GetSessionLengthLimit() = 0;
+
   // Creates a dummy delegate for testing.
   static SystemTrayDelegate* CreateDummyDelegate();
 };
 
 }  // namespace ash
 
 #endif  // ASH_SYSTEM_TRAY_SYSTEM_TRAY_DELEGATE_H_