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

ash/system/user/tray_user.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/user/tray_user.h"
 
 #include "ash/shell.h"
 #include "ash/system/tray/system_tray_delegate.h"
 #include "ash/system/tray/tray_constants.h"
 #include "ash/system/tray/tray_item_view.h"
@@ skipping 221 matching lines @@
   views::Label* username_;
   views::Label* email_;
 
   views::Button* signout_;
 
   DISALLOW_COPY_AND_ASSIGN(UserView);
 };
 
 }  // namespace tray
 
-TrayUser::TrayUser()
-    : user_(NULL),
+TrayUser::TrayUser(SystemTray* system_tray)
+    : SystemTrayItem(system_tray),
+      user_(NULL),
       avatar_(NULL),
       label_(NULL) {
 }
 
 TrayUser::~TrayUser() {
 }
 
 views::View* TrayUser::CreateTrayView(user::LoginStatus status) {
   CHECK(avatar_ == NULL);
   CHECK(label_ == NULL);
@@ skipping 86 matching lines @@
   // Check for null to avoid crbug.com/150944.
   if (avatar_) {
     avatar_->SetImage(
         ash::Shell::GetInstance()->tray_delegate()->GetUserImage(),
         gfx::Size(kUserIconSize, kUserIconSize));
   }
 }
 
 }  // namespace internal
 }  // namespace ash