Stop using shell::GetInstance()->system_tray() in system tray items

ash/system/bluetooth/tray_bluetooth.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_BLUETOOTH_TRAY_BLUETOOTH_H_
 #define ASH_SYSTEM_BLUETOOTH_TRAY_BLUETOOTH_H_
 
 #include "ash/system/bluetooth/bluetooth_observer.h"
 #include "ash/system/tray/system_tray_item.h"
 
 namespace ash {
+
+class SystemTray;
+
 namespace internal {
 
 namespace tray {
 class BluetoothDefaultView;
 class BluetoothDetailedView;
 }
 
 class TrayBluetooth : public SystemTrayItem,
                       public BluetoothObserver {
  public:
-  TrayBluetooth();
+  explicit TrayBluetooth(SystemTray* system_tray);
   virtual ~TrayBluetooth();
 
  private:
   // Overridden from SystemTrayItem.
   virtual views::View* CreateTrayView(user::LoginStatus status) OVERRIDE;
   virtual views::View* CreateDefaultView(user::LoginStatus status) OVERRIDE;
   virtual views::View* CreateDetailedView(user::LoginStatus status) OVERRIDE;
   virtual void DestroyTrayView() OVERRIDE;
   virtual void DestroyDefaultView() OVERRIDE;
   virtual void DestroyDetailedView() OVERRIDE;
   virtual void UpdateAfterLoginStatusChange(user::LoginStatus status) OVERRIDE;
 
   // Overridden from BluetoothObserver.
   virtual void OnBluetoothRefresh() OVERRIDE;
   virtual void OnBluetoothDiscoveringChanged() OVERRIDE;
 
   tray::BluetoothDefaultView* default_;
   tray::BluetoothDetailedView* detailed_;
 
   DISALLOW_COPY_AND_ASSIGN(TrayBluetooth);
 };
 
 }  // namespace internal
 }  // namespace ash
 
 #endif  // ASH_SYSTEM_BLUETOOTH_TRAY_BLUETOOTH_H_