Replace NULL with nullptr in all C++ files.

webrtc/modules/audio_coding/test/delay_test.cc

 /*
  *  Copyright (c) 2013 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 52 matching lines @@
 class DelayTest {
  public:
   DelayTest()
       : acm_a_(AudioCodingModule::Create(0)),
         acm_b_(AudioCodingModule::Create(1)),
         channel_a2b_(new Channel),
         test_cntr_(0),
         encoding_sample_rate_hz_(8000) {}
 
   ~DelayTest() {
-    if (channel_a2b_ != NULL) {
+    if (channel_a2b_ != nullptr) {
       delete channel_a2b_;
-      channel_a2b_ = NULL;
+      channel_a2b_ = nullptr;
     }
     in_file_a_.Close();
   }
 
   void Initialize() {
     test_cntr_ = 0;
     std::string file_name = webrtc::test::ResourcePath(
         "audio_coding/testfile32kHz", "pcm");
     if (FLAGS_input_file.size() > 0)
       file_name = FLAGS_input_file;
@@ skipping 174 matching lines @@
   test_setting.codec.num_channels = FLAGS_num_channels;
   test_setting.acm.dtx = FLAGS_dtx;
   test_setting.acm.fec = FLAGS_fec;
   test_setting.packet_loss = FLAGS_packet_loss;
 
   webrtc::DelayTest delay_test;
   delay_test.Initialize();
   delay_test.Perform(&test_setting, 1, 240, "delay_test");
   return 0;
 }