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

ash/system/logout_button/tray_logout_button.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/logout_button/tray_logout_button.h"
 
 #include <cstddef>
 
 #include "ash/shell.h"
 #include "ash/system/tray/system_tray_delegate.h"
@@ skipping 98 matching lines @@
   }
 
   user::LoginStatus login_status_;
   bool show_logout_button_in_tray_;
 
   DISALLOW_COPY_AND_ASSIGN(LogoutButton);
 };
 
 }  // namespace tray
 
-TrayLogoutButton::TrayLogoutButton() : logout_button_(NULL) {
+TrayLogoutButton::TrayLogoutButton(SystemTray* system_tray)
+    : SystemTrayItem(system_tray),
+      logout_button_(NULL) {
 }
 
 views::View* TrayLogoutButton::CreateTrayView(user::LoginStatus status) {
   CHECK(logout_button_ == NULL);
   logout_button_ = new tray::LogoutButton(status);
   return logout_button_;
 }
 
 void TrayLogoutButton::DestroyTrayView() {
   logout_button_ = NULL;
 }
 
 void TrayLogoutButton::UpdateAfterLoginStatusChange(user::LoginStatus status) {
   logout_button_->OnLoginStatusChanged(status);
 }
 
 void TrayLogoutButton::OnShowLogoutButtonInTrayChanged(bool show) {
   logout_button_->OnShowLogoutButtonInTrayChanged(show);
 }
 
 }  // namespace internal
 }  // namespace ash