Delete class NullRtpData and function NullObjectRtpData

webrtc/modules/rtp_rtcp/test/testAPI/test_api.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.
  */
 #ifndef WEBRTC_MODULES_RTP_RTCP_TEST_TESTAPI_TEST_API_H_
@@ skipping 33 matching lines @@
 
  private:
   int count_;
   int packet_loss_;
   ReceiveStatistics* receive_statistics_;
   RTPPayloadRegistry* rtp_payload_registry_;
   RtpReceiver* rtp_receiver_;
   RtpRtcp* rtp_rtcp_module_;
 };
 
-class TestRtpReceiver : public NullRtpData {
+class TestRtpReceiver : public RtpData {
  public:
   int32_t OnReceivedPayloadData(
       const uint8_t* payload_data,
       size_t payload_size,
       const webrtc::WebRtcRTPHeader* rtp_header) override;
 
   const uint8_t* payload_data() const { return payload_data_; }
   size_t payload_size() const { return payload_size_; }
   webrtc::WebRtcRTPHeader rtp_header() const { return rtp_header_; }
 
  private:
   uint8_t payload_data_[1500];
   size_t payload_size_;
   webrtc::WebRtcRTPHeader rtp_header_;
 };
 
 }  // namespace webrtc
 #endif  // WEBRTC_MODULES_RTP_RTCP_TEST_TESTAPI_TEST_API_H_