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

ash/system/chromeos/tray_display.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_CHROMEOS_TRAY_DISPLAY_H_
 #define ASH_SYSTEM_CHROMEOS_TRAY_DISPLAY_H_
 
 #include "ash/system/tray/system_tray_item.h"
 #include "base/memory/scoped_ptr.h"
 #include "ui/gfx/display_observer.h"
 
 #include "chromeos/display/output_configurator.h"
 
 namespace views {
 class View;
 }
 
 namespace ash {
-
 namespace internal {
 class DisplayView;
 
 class TrayDisplay : public SystemTrayItem,
                     public chromeos::OutputConfigurator::Observer,
                     public gfx::DisplayObserver {
  public:
-  TrayDisplay();
+  explicit TrayDisplay(SystemTray* system_tray);
   virtual ~TrayDisplay();
 
  private:
   // Overridden from SystemTrayItem.
   virtual views::View* CreateDefaultView(user::LoginStatus status) OVERRIDE;
   virtual void DestroyDefaultView() OVERRIDE;
 
   // Overridden from aura::DisplayObserver
   virtual void OnDisplayBoundsChanged(const gfx::Display& display) OVERRIDE;
   virtual void OnDisplayAdded(const gfx::Display& new_display) OVERRIDE;
   virtual void OnDisplayRemoved(const gfx::Display& old_display) OVERRIDE;
 
   // Overridden from chromeos::OutputConfigurator::Observer
   virtual void OnDisplayModeChanged() OVERRIDE;
 
   DisplayView* default_;
 
   DISALLOW_COPY_AND_ASSIGN(TrayDisplay);
 };
 
 }  // namespace internal
 }  // namespace ash
 
 #endif  // ASH_SYSTEM_CHROMEOS_TRAY_DISPLAY_H_