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

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_
 #pragma once
 
 #include <string>
 #include <vector>
@@ skipping 41 matching lines @@
 };
 
 typedef std::vector<IMEInfo> IMEInfoList;
 
 struct PowerSupplyStatus;
 
 class SystemTrayDelegate {
  public:
   virtual ~SystemTrayDelegate() {}
 
+  // Returns true if system tray should be visible on startup.
+  virtual bool GetTrayVisibilityOnStartup() = 0;
+
   // Gets information about the logged in user.
   virtual const std::string GetUserDisplayName() const = 0;
   virtual const std::string GetUserEmail() const = 0;
   virtual const SkBitmap& GetUserImage() const = 0;
   virtual user::LoginStatus GetUserLoginStatus() const = 0;
 
   // Returns whether a system upgrade is available.
   virtual bool SystemShouldUpgrade() const = 0;
 
   // Returns the resource id for the icon to show for the update notification.
@@ skipping 97 matching lines @@
   // Returns whether bluetooth is enabled.
   virtual bool GetBluetoothEnabled() = 0;
 
   // Shows UI for changing proxy settings.
   virtual void ChangeProxySettings() = 0;
 };
 
 }  // namespace ash
 
 #endif  // ASH_SYSTEM_TRAY_SYSTEM_TRAY_DELEGATE_H_