Added more error checking for audio packets.

remoting/codec/audio_decoder.h

 // 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.
 
 #ifndef REMOTING_CODEC_AUDIO_DECODER_H_
 #define REMOTING_CODEC_AUDIO_DECODER_H_
 
 #include "base/memory/scoped_ptr.h"
 
 namespace remoting {
 
 namespace protocol {
 class SessionConfig;
 }  // namespace protocol
 
 class AudioPacket;
 
 class AudioDecoder {
  public:
   static scoped_ptr<AudioDecoder> CreateAudioDecoder(
       const protocol::SessionConfig& config);
 
   virtual ~AudioDecoder() {}
 
+  // Returns the decoded packet. If the packet is invalid, then a NULL
+  // scoped_ptr is returned.
   virtual scoped_ptr<AudioPacket> Decode(scoped_ptr<AudioPacket> packet) = 0;
 };
 
 }  // namespace remoting
 
 #endif  // REMOTING_CODEC_AUDIO_DECODER_H_