Remove ash_shell audio system tray item on Windows.

ash/system/win/audio/tray_audio_win.cc

-// Copyright 2014 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/win/audio/tray_audio_win.h"
-
-#include <memory>
-
-#include "ash/system/win/audio/tray_audio_delegate_win.h"
-
-namespace ash {
-
-using system::TrayAudioDelegate;
-using system::TrayAudioDelegateWin;
-
-TrayAudioWin::TrayAudioWin(SystemTray* system_tray)
-    : TrayAudio(
-          system_tray,
-          std::unique_ptr<TrayAudioDelegate>(new TrayAudioDelegateWin())) {}
-
-TrayAudioWin::~TrayAudioWin() {
-}
-
-}  // namespace ash