Remove dead code (we no longer support SILK)

webrtc/voice_engine/voe_codec_impl.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 47 matching lines @@
 
   int SetOpusDtx(int channel, bool enable_dtx) override;
 
   RtcEventLog* GetEventLog() override;
 
  protected:
   VoECodecImpl(voe::SharedData* shared);
   ~VoECodecImpl() override;
 
  private:
-  void ACMToExternalCodecRepresentation(CodecInst& toInst,
-                                        const CodecInst& fromInst);
-
-  void ExternalToACMCodecRepresentation(CodecInst& toInst,
-                                        const CodecInst& fromInst);
-
   voe::SharedData* _shared;
 };
 
 }  // namespace webrtc
 
 #endif  // WEBRTC_VOICE_ENGINE_VOE_CODEC_IMPL_H