Replace NULL with nullptr in all C++ files.

webrtc/test/testsupport/frame_writer.cc

 /*
  *  Copyright (c) 2011 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.
  */
 
 #include "webrtc/test/testsupport/frame_writer.h"
 
 #include <assert.h>
 
 namespace webrtc {
 namespace test {
 
 FrameWriterImpl::FrameWriterImpl(std::string output_filename,
                                  size_t frame_length_in_bytes)
     : output_filename_(output_filename),
       frame_length_in_bytes_(frame_length_in_bytes),
-      output_file_(NULL) {
-}
+      output_file_(nullptr) {}
 
 FrameWriterImpl::~FrameWriterImpl() {
   Close();
 }
 
 bool FrameWriterImpl::Init() {
   if (frame_length_in_bytes_ <= 0) {
     fprintf(stderr, "Frame length must be >0, was %zu\n",
             frame_length_in_bytes_);
     return false;
   }
   output_file_ = fopen(output_filename_.c_str(), "wb");
-  if (output_file_ == NULL) {
+  if (output_file_ == nullptr) {
     fprintf(stderr, "Couldn't open output file for writing: %s\n",
             output_filename_.c_str());
     return false;
   }
   return true;
 }
 
 void FrameWriterImpl::Close() {
-  if (output_file_ != NULL) {
+  if (output_file_ != nullptr) {
     fclose(output_file_);
-    output_file_ = NULL;
+    output_file_ = nullptr;
   }
 }
 
 size_t FrameWriterImpl::FrameLength() { return frame_length_in_bytes_; }
 
 bool FrameWriterImpl::WriteFrame(uint8_t* frame_buffer) {
   assert(frame_buffer);
-  if (output_file_ == NULL) {
-    fprintf(stderr, "FrameWriter is not initialized (output file is NULL)\n");
+  if (output_file_ == nullptr) {
+    fprintf(stderr, "FrameWriter is not initialized (output file is null)\n");
     return false;
   }
   size_t bytes_written = fwrite(frame_buffer, 1, frame_length_in_bytes_,
                                 output_file_);
   if (bytes_written != frame_length_in_bytes_) {
     fprintf(stderr, "Failed to write %zu bytes to file %s\n",
             frame_length_in_bytes_, output_filename_.c_str());
     return false;
   }
   return true;
 }
 
 }  // namespace test
 }  // namespace webrtc