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

ash/system/chromeos/tray_display.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/chromeos/tray_display.h"
 
 #include "ash/display/display_controller.h"
 #include "ash/display/display_manager.h"
 #include "ash/screen_ash.h"
 #include "ash/shell.h"
@@ skipping 96 matching lines @@
 
     return true;
   }
 
   user::LoginStatus login_status_;
   views::Label* label_;
 
   DISALLOW_COPY_AND_ASSIGN(DisplayView);
 };
 
-TrayDisplay::TrayDisplay()
-    : default_(NULL) {
+TrayDisplay::TrayDisplay(SystemTray* system_tray)
+    : SystemTrayItem(system_tray),
+      default_(NULL) {
   Shell::GetScreen()->AddObserver(this);
   Shell::GetInstance()->output_configurator()->AddObserver(this);
 }
 
 TrayDisplay::~TrayDisplay() {
   Shell::GetScreen()->RemoveObserver(this);
   Shell::GetInstance()->output_configurator()->RemoveObserver(this);
 }
 
 views::View* TrayDisplay::CreateDefaultView(user::LoginStatus status) {
@@ skipping 20 matching lines @@
     default_->Update();
 }
 
 void TrayDisplay::OnDisplayModeChanged() {
   if (default_)
     default_->Update();
 }
 
 }  // namespace internal
 }  // namespace ash