Use mojo volume interfaces for mash and classic ash.

ash/common/system/tray/default_system_tray_delegate.cc

 // Copyright 2013 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/common/system/tray/default_system_tray_delegate.h"
 
 #include <string>
 #include <utility>
 
 #include "ash/common/system/networking_config_delegate.h"
-#include "ash/common/system/volume_control_delegate.h"
 #include "base/message_loop/message_loop.h"
 #include "base/time/time.h"
 
 namespace ash {
 
 DefaultSystemTrayDelegate::DefaultSystemTrayDelegate()
     : bluetooth_enabled_(true) {}
 
 DefaultSystemTrayDelegate::~DefaultSystemTrayDelegate() {}
 
@@ skipping 35 matching lines @@
 }
 
 bool DefaultSystemTrayDelegate::GetBluetoothEnabled() {
   return bluetooth_enabled_;
 }
 
 bool DefaultSystemTrayDelegate::GetBluetoothDiscovering() {
   return false;
 }
 
-VolumeControlDelegate* DefaultSystemTrayDelegate::GetVolumeControlDelegate()
-    const {
-  return volume_control_delegate_.get();
-}
-
-void DefaultSystemTrayDelegate::SetVolumeControlDelegate(
-    std::unique_ptr<VolumeControlDelegate> delegate) {
-  volume_control_delegate_ = std::move(delegate);
-}
-
 int DefaultSystemTrayDelegate::GetSystemTrayMenuWidth() {
   // This is the default width for English languages.
   return 300;
 }
 
 }  // namespace ash