Use mojo volume interfaces for mash and classic ash.

ash/common/system/tray/system_tray_delegate.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/common/system/tray/system_tray_delegate.h"
 
 #include "ash/common/system/tray/ime_info.h"
 #include "ash/common/system/tray/system_tray_item.h"
 
 namespace ash {
@@ skipping 124 matching lines @@
 
 CastConfigDelegate* SystemTrayDelegate::GetCastConfigDelegate() {
   return nullptr;
 }
 
 NetworkingConfigDelegate* SystemTrayDelegate::GetNetworkingConfigDelegate()
     const {
   return nullptr;
 }
 
-VolumeControlDelegate* SystemTrayDelegate::GetVolumeControlDelegate() const {
-  return nullptr;
-}
-
-void SystemTrayDelegate::SetVolumeControlDelegate(
-    std::unique_ptr<VolumeControlDelegate> delegate) {}
-
 bool SystemTrayDelegate::GetSessionStartTime(
     base::TimeTicks* session_start_time) {
   return false;
 }
 
 bool SystemTrayDelegate::GetSessionLengthLimit(
     base::TimeDelta* session_length_limit) {
   return false;
 }
 
@@ skipping 25 matching lines @@
 VPNDelegate* SystemTrayDelegate::GetVPNDelegate() const {
   return nullptr;
 }
 
 std::unique_ptr<SystemTrayItem> SystemTrayDelegate::CreateRotationLockTrayItem(
     SystemTray* tray) {
   return nullptr;
 }
 
 }  // namespace ash