Replace NULL with nullptr or null in webrtc/audio/ and common_audio/.

webrtc/common_audio/wav_file.cc

 /*
  *  Copyright (c) 2014 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 89 matching lines @@
     chunk = ReadSamples(chunk, isamples);
     for (size_t j = 0; j < chunk; ++j)
       samples[i + j] = isamples[j];
     read += chunk;
   }
   return read;
 }
 
 void WavReader::Close() {
   RTC_CHECK_EQ(0, fclose(file_handle_));
-  file_handle_ = NULL;
+  file_handle_ = nullptr;
 }
 
 WavWriter::WavWriter(const std::string& filename, int sample_rate,
                      size_t num_channels)
     : sample_rate_(sample_rate),
       num_channels_(num_channels),
       num_samples_(0),
       file_handle_(fopen(filename.c_str(), "wb")) {
   RTC_CHECK(file_handle_) << "Could not open wav file for writing.";
   RTC_CHECK(CheckWavParameters(num_channels_, sample_rate_, kWavFormat,
@@ skipping 42 matching lines @@
   }
 }
 
 void WavWriter::Close() {
   RTC_CHECK_EQ(0, fseek(file_handle_, 0, SEEK_SET));
   uint8_t header[kWavHeaderSize];
   WriteWavHeader(header, num_channels_, sample_rate_, kWavFormat,
                  kBytesPerSample, num_samples_);
   RTC_CHECK_EQ(1, fwrite(header, kWavHeaderSize, 1, file_handle_));
   RTC_CHECK_EQ(0, fclose(file_handle_));
-  file_handle_ = NULL;
+  file_handle_ = nullptr;
 }
 
 }  // namespace webrtc
 
 rtc_WavWriter* rtc_WavOpen(const char* filename,
                            int sample_rate,
                            size_t num_channels) {
   return reinterpret_cast<rtc_WavWriter*>(
       new webrtc::WavWriter(filename, sample_rate, num_channels));
 }
@@ skipping 12 matching lines @@
   return reinterpret_cast<const webrtc::WavWriter*>(wf)->sample_rate();
 }
 
 size_t rtc_WavNumChannels(const rtc_WavWriter* wf) {
   return reinterpret_cast<const webrtc::WavWriter*>(wf)->num_channels();
 }
 
 size_t rtc_WavNumSamples(const rtc_WavWriter* wf) {
   return reinterpret_cast<const webrtc::WavWriter*>(wf)->num_samples();
 }