Remove webrtc/sound/ subdir.

webrtc/sound/nullsoundsystemfactory.h

-/*
- *  Copyright 2004 The WebRTC Project Authors. All rights reserved.
- *
- *  Use of this source code is governed by a BSD-style license
- *  that can be found in the LICENSE file in the root of the source
- *  tree. An additional intellectual property rights grant can be found
- *  in the file PATENTS.  All contributing project authors may
- *  be found in the AUTHORS file in the root of the source tree.
- */
-
-#ifndef WEBRTC_SOUND_NULLSOUNDSYSTEMFACTORY_H_
-#define WEBRTC_SOUND_NULLSOUNDSYSTEMFACTORY_H_
-
-#include "webrtc/sound/soundsystemfactory.h"
-
-namespace rtc {
-
-// A SoundSystemFactory that always returns a NullSoundSystem. Intended for
-// testing.
-class NullSoundSystemFactory : public SoundSystemFactory {
- public:
-  NullSoundSystemFactory();
-  ~NullSoundSystemFactory() override;
-
- protected:
-  // Inherited from SoundSystemFactory.
-  bool SetupInstance() override;
-  void CleanupInstance() override;
-};
-
-}  // namespace rtc
-
-#endif  // WEBRTC_SOUND_NULLSOUNDSYSTEMFACTORY_H_