Delete class NullRtpData and function NullObjectRtpData

webrtc/modules/rtp_rtcp/test/testAPI/test_api_audio.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 29 matching lines @@
 
 bool IsComfortNoisePayload(uint8_t payload_type) {
   for (const auto& c : kCngCodecs) {
     if (c.payload_type == payload_type)
       return true;
   }
 
   return false;
 }
 
-class VerifyingAudioReceiver : public NullRtpData {
+class VerifyingAudioReceiver : public RtpData {
  public:
   int32_t OnReceivedPayloadData(
       const uint8_t* payloadData,
       size_t payloadSize,
       const webrtc::WebRtcRTPHeader* rtpHeader) override {
     const uint8_t payload_type = rtpHeader->header.payloadType;
     if (payload_type == kPcmuPayloadType || payload_type == kDtmfPayloadType) {
       EXPECT_EQ(sizeof(kTestPayload), payloadSize);
       // All our test vectors for PCMU and DTMF are equal to |kTestPayload|.
       const size_t min_size = std::min(sizeof(kTestPayload), payloadSize);
@@ skipping 217 matching lines @@
                                           nullptr, nullptr, nullptr));
 
     EXPECT_EQ(test_ssrc, rtp_receiver2_->SSRC());
     EXPECT_TRUE(rtp_receiver2_->Timestamp(&timestamp));
     EXPECT_EQ(test_timestamp + in_timestamp, timestamp);
     in_timestamp += 10;
   }
 }
 
 }  // namespace webrtc