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

chrome/browser/chromeos/system/ash_system_tray_delegate.cc

Index: chrome/browser/chromeos/system/ash_system_tray_delegate.cc
diff --git a/chrome/browser/chromeos/system/ash_system_tray_delegate.cc b/chrome/browser/chromeos/system/ash_system_tray_delegate.cc
index ac0bd6415b3b8b5c17d0daaefe7eef3e534060b4..7227f200fd182860ef690a04a724a0daf16602ed 100644
--- a/chrome/browser/chromeos/system/ash_system_tray_delegate.cc
+++ b/chrome/browser/chromeos/system/ash_system_tray_delegate.cc
@@ -861,6 +861,10 @@ class SystemTrayDelegate : public ash::SystemTrayDelegate,
         base::Bind(&SystemTrayDelegate::UpdateShowLogoutButtonInTray,
                    base::Unretained(this)));
     user_pref_registrar_->Add(
+        prefs::kLogoutDialogDurationMs,
+        base::Bind(&SystemTrayDelegate::UpdateLogoutDialogDuration,
+                   base::Unretained(this)));
+    user_pref_registrar_->Add(
         prefs::kLargeCursorEnabled,
         base::Bind(&SystemTrayDelegate::OnAccessibilityModeChanged,
                    base::Unretained(this),
@@ -877,6 +881,7 @@ class SystemTrayDelegate : public ash::SystemTrayDelegate,
 
     UpdateClockType();
     UpdateShowLogoutButtonInTray();
+    UpdateLogoutDialogDuration();
     UpdatePerformanceTracing();
     search_key_mapped_to_ =
         profile->GetPrefs()->GetInteger(prefs::kLanguageRemapSearchKeyTo);
@@ -948,6 +953,12 @@ class SystemTrayDelegate : public ash::SystemTrayDelegate,
             prefs::kShowLogoutButtonInTray));
   }
 
+  void UpdateLogoutDialogDuration() {
+    GetSystemTrayNotifier()->NotifyLogoutDialogDurationChanged(
+        user_pref_registrar_->prefs()->GetInteger(

[bartfab (slow), 2013/12/03 19:46:04]

Nit: Why not convert to base::TimeDelta() here? You have to do the conversion
somewhere - best do it as early as possible so the value you pass around is as
unambiguous as possible.

[binjin, 2013/12/04 10:47:03]

Done.

+            prefs::kLogoutDialogDurationMs));
+  }
+
   void UpdateSessionStartTime() {
     const PrefService* local_state = local_state_registrar_->prefs();
     if (local_state->HasPrefPath(prefs::kSessionStartTime)) {