Convert CNG into C++ and remove it from AudioDecoder

webrtc/modules/audio_coding/neteq/mock/mock_decoder_database.h

 /*
  *  Copyright (c) 2012 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.
  */
 
@@ skipping 41 matching lines @@
       bool(uint8_t rtp_payload_type));
   MOCK_CONST_METHOD1(IsRed,
       bool(uint8_t rtp_payload_type));
   MOCK_METHOD2(SetActiveDecoder,
       int(uint8_t rtp_payload_type, bool* new_decoder));
   MOCK_METHOD0(GetActiveDecoder,
       AudioDecoder*());
   MOCK_METHOD1(SetActiveCngDecoder,
       int(uint8_t rtp_payload_type));
   MOCK_METHOD0(GetActiveCngDecoder,
-      AudioDecoder*());
+      ComfortNoiseDecoder*());
   MOCK_CONST_METHOD1(CheckPayloadTypes,
       int(const PacketList& packet_list));
 };
 
 }  // namespace webrtc
 #endif  // WEBRTC_MODULES_AUDIO_CODING_NETEQ_MOCK_MOCK_DECODER_DATABASE_H_