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

chrome/browser/ui/ash/chrome_launcher_prefs.cc

Index: chrome/browser/ui/ash/chrome_launcher_prefs.cc
diff --git a/chrome/browser/ui/ash/chrome_launcher_prefs.cc b/chrome/browser/ui/ash/chrome_launcher_prefs.cc
index 87c923ceddb8e62fa88105b096ff89afbbaab8da..b02441e1d1b1c8e4ec469668e07d252a64936bab 100644
--- a/chrome/browser/ui/ash/chrome_launcher_prefs.cc
+++ b/chrome/browser/ui/ash/chrome_launcher_prefs.cc
@@ -68,13 +68,17 @@ void RegisterChromeLauncherUserPrefs(
       prefs::kShelfAlignmentLocal,
       std::string(),
       user_prefs::PrefRegistrySyncable::UNSYNCABLE_PREF);
+  registry->RegisterDictionaryPref(
+      prefs::kShelfPreferences,
+      user_prefs::PrefRegistrySyncable::UNSYNCABLE_PREF);
+  registry->RegisterIntegerPref(
+      prefs::kLogoutDialogDurationMs,
+      20000,
+      user_prefs::PrefRegistrySyncable::UNSYNCABLE_PREF);
   registry->RegisterBooleanPref(
       prefs::kShowLogoutButtonInTray,
       false,
       user_prefs::PrefRegistrySyncable::UNSYNCABLE_PREF);
-  registry->RegisterDictionaryPref(
-      prefs::kShelfPreferences,
-      user_prefs::PrefRegistrySyncable::UNSYNCABLE_PREF);
 }
 
 base::DictionaryValue* CreateAppDict(const std::string& app_id) {