Implements the dialog view for logout button tray in public sessions.

ash/system/logout_button/logout_button_observer.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_LOGOUT_BUTTON_LOGOUT_BUTTON_OBSERVER_H_
 #define ASH_SYSTEM_LOGOUT_BUTTON_LOGOUT_BUTTON_OBSERVER_H_
 
 namespace ash {
 
-// Observer for the value of the kShowLogoutButtonInTray pref that determines
-// whether a logout button should be shown in the system tray during a session.
+// Observer for the values of the kShowLogoutButtonInTray pref and
+// kLogoutDialogDurationMs prefs. kShowLogoutButtonInTray determines whether a
+// logout button should be shown in the system tray during a session.
+// kLogoutDialogDurationMs is the duration in milliseconds of the logout
+// confirmation dialog after user pressed logout button.
 class LogoutButtonObserver {
  public:
   virtual ~LogoutButtonObserver() {}
 
   // Called when the value of the kShowLogoutButtonInTray pref changes.
   virtual void OnShowLogoutButtonInTrayChanged(bool show) = 0;
+
+  // Called when the value of the kLogoutDialogDurationMs pref changes.
+  virtual void OnLogoutDialogDurationChanged(int duration) = 0;

[bartfab (slow), 2013/10/30 11:17:28]

I think the conversion should happen at a lower level. This is an interface for
passing configuration settings to the power button. The fact that these settings
come from prefs is an implementation detail. The settings should be read from
their source (a pref in this case), converted to the most appropriate data
format (base::TimeDelta in this case) and then sent to the button.

[binjin, 2013/11/19 14:43:46]

Done.

 };
 
 }  // namespace ash
 
 #endif  // ASH_SYSTEM_LOGOUT_BUTTON_LOGOUT_BUTTON_OBSERVER_H_