Convert CNG into C++ and remove it from AudioDecoder

webrtc/modules/audio_coding/neteq/comfort_noise.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 20 matching lines @@
     kInternalError,
     kMultiChannelNotSupported
   };
 
   ComfortNoise(int fs_hz, DecoderDatabase* decoder_database,
                SyncBuffer* sync_buffer)
       : fs_hz_(fs_hz),
         first_call_(true),
         overlap_length_(5 * fs_hz_ / 8000),
         decoder_database_(decoder_database),
-        sync_buffer_(sync_buffer),
-        internal_error_code_(0) {
+        sync_buffer_(sync_buffer) {
   }
 
   // Resets the state. Should be called before each new comfort noise period.
   void Reset();
 
   // Update the comfort noise generator with the parameters in |packet|.
   // Will delete the packet.
   int UpdateParameters(Packet* packet);
 
   // Generates |requested_length| samples of comfort noise and writes to
@@ skipping 11 matching lines @@
   bool first_call_;
   size_t overlap_length_;
   DecoderDatabase* decoder_database_;
   SyncBuffer* sync_buffer_;
   int internal_error_code_;
   RTC_DISALLOW_COPY_AND_ASSIGN(ComfortNoise);
 };
 
 }  // namespace webrtc
 #endif  // WEBRTC_MODULES_AUDIO_CODING_NETEQ_COMFORT_NOISE_H_