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

ash/system/tray/tray_empty.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/tray/tray_empty.h"
 
 #include "ui/views/layout/box_layout.h"
 #include "ui/views/background.h"
 #include "ui/views/view.h"
 
 namespace {
 
 class EmptyBackground : public views::Background {
  public:
   EmptyBackground() {}
   virtual ~EmptyBackground() {}
 
  private:
   virtual void Paint(gfx::Canvas* canvas, views::View* view) const OVERRIDE {
   }
 
   DISALLOW_COPY_AND_ASSIGN(EmptyBackground);
 };
 
 }
 
 namespace ash {
 namespace internal {
 
-TrayEmpty::TrayEmpty() {}
+TrayEmpty::TrayEmpty(SystemTray* system_tray)
+    : SystemTrayItem(system_tray) {
+}
 
 TrayEmpty::~TrayEmpty() {}
 
 views::View* TrayEmpty::CreateTrayView(user::LoginStatus status) {
   return NULL;
 }
 
 views::View* TrayEmpty::CreateDefaultView(user::LoginStatus status) {
   if (status == user::LOGGED_IN_NONE)
     return NULL;
@@ skipping 15 matching lines @@
 void TrayEmpty::DestroyTrayView() {}
 
 void TrayEmpty::DestroyDefaultView() {}
 
 void TrayEmpty::DestroyDetailedView() {}
 
 void TrayEmpty::UpdateAfterLoginStatusChange(user::LoginStatus status) {}
 
 }  // namespace internal
 }  // namespace ash