Enable the volume slider in Ash for windows.

ash/system/win/audio/tray_audio_win.cc

Index: ash/system/win/audio/tray_audio_win.cc
diff --git a/ash/system/win/audio/tray_audio_win.cc b/ash/system/win/audio/tray_audio_win.cc
new file mode 100644
index 0000000000000000000000000000000000000000..0d2226c02523261c7cec25e64f164c9c9243dc69
--- /dev/null
+++ b/ash/system/win/audio/tray_audio_win.cc
@@ -0,0 +1,25 @@
+// 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 "ash/system/win/audio/tray_audio_delegate_win.h"
+
+namespace ash {
+
+using system::TrayAudioDelegate;
+using system::TrayAudioDelegateWin;
+
+namespace internal {
+
+TrayAudioWin::TrayAudioWin(SystemTray* system_tray)
+    : TrayAudio(system_tray,
+                scoped_ptr<TrayAudioDelegate>(new TrayAudioDelegateWin())) {
+}
+
+TrayAudioWin::~TrayAudioWin() {
+}
+
+}  // namespace internal
+}  // namespace ash