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

webrtc/modules/rtp_rtcp/test/testAPI/test_api.cc

 /*
  *  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 134 matching lines @@
   module_->SetRTCPStatus(RtcpMode::kCompound);
   EXPECT_EQ(RtcpMode::kCompound, module_->RTCP());
 
   EXPECT_EQ(0, module_->SetCNAME("john.doe@test.test"));
 
   EXPECT_FALSE(module_->TMMBR());
   module_->SetTMMBRStatus(true);
   EXPECT_TRUE(module_->TMMBR());
   module_->SetTMMBRStatus(false);
   EXPECT_FALSE(module_->TMMBR());
-
-  EXPECT_EQ(kNackOff, rtp_receiver_->NACK());
-  rtp_receiver_->SetNACKStatus(kNackRtcp);
-  EXPECT_EQ(kNackRtcp, rtp_receiver_->NACK());
 }
 
 TEST_F(RtpRtcpAPITest, RtxSender) {
   module_->SetRtxSendStatus(kRtxRetransmitted);
   EXPECT_EQ(kRtxRetransmitted, module_->RtxSendStatus());
 
   module_->SetRtxSendStatus(kRtxOff);
   EXPECT_EQ(kRtxOff, module_->RtxSendStatus());
 
   module_->SetRtxSendStatus(kRtxRetransmitted);
@@ skipping 13 matching lines @@
   rtx_header.payloadType = kRtxPayloadType;
   EXPECT_TRUE(rtp_payload_registry_->IsRtx(rtx_header));
   rtx_header.ssrc = 0;
   EXPECT_FALSE(rtp_payload_registry_->IsRtx(rtx_header));
   rtx_header.ssrc = kRtxSsrc;
   rtx_header.payloadType = 0;
   EXPECT_TRUE(rtp_payload_registry_->IsRtx(rtx_header));
 }
 
 }  // namespace webrtc