Convert CNG into C++ and remove it from AudioDecoder

webrtc/modules/audio_coding/neteq/normal.cc

Index: webrtc/modules/audio_coding/neteq/normal.cc
diff --git a/webrtc/modules/audio_coding/neteq/normal.cc b/webrtc/modules/audio_coding/neteq/normal.cc
index 9bddfe77657924f6faa389e05b021ec1b700765c..1d286150e25b7fec93f07503b153a9a3d7d096d8 100644
--- a/webrtc/modules/audio_coding/neteq/normal.cc
+++ b/webrtc/modules/audio_coding/neteq/normal.cc
@@ -149,11 +149,11 @@ int Normal::Process(const int16_t* input,
     int16_t cng_output[kCngLength];
     // Reset mute factor and start up fresh.
     external_mute_factor_array[0] = 16384;
-    AudioDecoder* cng_decoder = decoder_database_->GetActiveCngDecoder();
+    CNG_dec_inst* cng_decoder = decoder_database_->GetActiveCngDecoder();
 
     if (cng_decoder) {
       // Generate long enough for 32kHz.
-      if (WebRtcCng_Generate(cng_decoder->CngDecoderInstance(), cng_output,
+      if (WebRtcCng_Generate(cng_decoder, cng_output,
                              kCngLength, 0) < 0) {
         // Error returned; set return vector to all zeros.
         memset(cng_output, 0, sizeof(cng_output));