Adding an interface to allow extension of the audio player for CRD and iOS.

remoting/client/audio_consumer.h

 // Copyright 2016 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.
 
 #ifndef REMOTING_CLIENT_AUDIO_CONSUMER_H_
 #define REMOTING_CLIENT_AUDIO_CONSUMER_H_
 
 #include <memory>
 
 namespace remoting {
 
 class AudioPacket;
 
 class AudioConsumer {
  public:
-  virtual ~AudioConsumer(){};
+  virtual void AddAudioPacket(std::unique_ptr<AudioPacket> packet) = 0;
 
-  virtual void AddAudioPacket(std::unique_ptr<AudioPacket> packet) = 0;
+ protected:
+  virtual ~AudioConsumer() {}
 };
 
 }  // namespace remoting
 
 #endif  // REMOTING_CLIENT_AUDIO_CONSUMER_H_