Removing some old code which looked like it had to do with NACK handling but in reality did nothing.

webrtc/modules/rtp_rtcp/mocks/mock_rtp_rtcp.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 184 matching lines @@
       bool());
   MOCK_METHOD1(SetREMBStatus, void(const bool enable));
   MOCK_METHOD2(SetREMBData,
                void(const uint32_t bitrate,
                     const std::vector<uint32_t>& ssrcs));
   MOCK_CONST_METHOD0(TMMBR,
       bool());
   MOCK_METHOD1(SetTMMBRStatus, void(const bool enable));
   MOCK_METHOD1(OnBandwidthEstimateUpdate,
       void(uint16_t bandWidthKbit));
-  MOCK_CONST_METHOD0(NACK,
-      NACKMethod());
-  MOCK_METHOD2(SetNACKStatus,
-      int32_t(const NACKMethod method, int oldestSequenceNumberToNack));
   MOCK_CONST_METHOD0(SelectiveRetransmissions,
       int());
   MOCK_METHOD1(SetSelectiveRetransmissions,
       int(uint8_t settings));
   MOCK_METHOD2(SendNACK,
       int32_t(const uint16_t* nackList, const uint16_t size));
   MOCK_METHOD1(SendNack, void(const std::vector<uint16_t>& sequence_numbers));
   MOCK_METHOD2(SetStorePacketsStatus,
                void(const bool enable, const uint16_t numberToStore));
   MOCK_CONST_METHOD0(StorePackets, bool());
@@ skipping 40 matching lines @@
       void(StreamDataCountersCallback*));
   MOCK_CONST_METHOD0(GetSendChannelRtpStatisticsCallback,
       StreamDataCountersCallback*(void));
   // Members.
   unsigned int remote_ssrc_;
 };
 
 }  // namespace webrtc
 
 #endif  // WEBRTC_MODULES_RTP_RTCP_MOCKS_MOCK_RTP_RTCP_H_