aura: Uber tray should not show up on start screen in kiosk mode.

ash/system/tray/system_tray.cc

 // 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.
 
 #include "ash/system/tray/system_tray.h"
 
 #include "ash/shell.h"
 #include "ash/shell/panel_window.h"
 #include "ash/shell_window_ids.h"
 #include "ash/system/tray/tray_constants.h"
@@ skipping 489 matching lines @@
   }
   container_->RemoveAllChildViews(true);
 
   for (std::vector<SystemTrayItem*>::iterator it = items_.begin();
       it != items_.end();
       ++it) {
     views::View* view = (*it)->CreateTrayView(login_status);
     if (view)
       container_->AddChildViewAt(new TrayItemContainer(view), 0);
   }
+  SetVisible(true);
   PreferredSizeChanged();
 }
 
 void SystemTray::SetPaintsBackground(
       bool value,
       internal::BackgroundAnimator::ChangeType change_type) {
   background_animator_.SetPaintsBackground(value, change_type);
 }
 
 void SystemTray::ShowItems(std::vector<SystemTrayItem*>& items,
@@ skipping 72 matching lines @@
 }
 
 void SystemTray::UpdateBackground(int alpha) {
   if (mouse_in_tray_)
     alpha += kTrayBackgroundHoverAlpha - kTrayBackgroundAlpha;
   background_->set_alpha(alpha);
   SchedulePaint();
 }
 
 }  // namespace ash