Replace NULL with nullptr in all C++ files.

webrtc/modules/video_coding/test/test_util.cc

Index: webrtc/modules/video_coding/test/test_util.cc
diff --git a/webrtc/modules/video_coding/test/test_util.cc b/webrtc/modules/video_coding/test/test_util.cc
index 386b4300a96a6c9c4226a380484243290ec95ccd..df29afdf1d43500723ac81ee982e99a0365adec1 100644
--- a/webrtc/modules/video_coding/test/test_util.cc
+++ b/webrtc/modules/video_coding/test/test_util.cc
@@ -69,8 +69,8 @@ FileOutputFrameReceiver::FileOutputFrameReceiver(
     const std::string& base_out_filename,
     uint32_t ssrc)
     : out_filename_(),
-      out_file_(NULL),
-      timing_file_(NULL),
+      out_file_(nullptr),
+      timing_file_(nullptr),
       width_(0),
       height_(0),
       count_(0) {
@@ -89,26 +89,26 @@ FileOutputFrameReceiver::FileOutputFrameReceiver(
 }
 
 FileOutputFrameReceiver::~FileOutputFrameReceiver() {
-  if (timing_file_ != NULL) {
+  if (timing_file_ != nullptr) {
     fclose(timing_file_);
   }
-  if (out_file_ != NULL) {
+  if (out_file_ != nullptr) {
     fclose(out_file_);
   }
 }
 
 int32_t FileOutputFrameReceiver::FrameToRender(webrtc::VideoFrame& video_frame,
                                                rtc::Optional<uint8_t> qp) {
-  if (timing_file_ == NULL) {
+  if (timing_file_ == nullptr) {
     std::string basename;
     std::string extension;
     SplitFilename(out_filename_, &basename, &extension);
     timing_file_ = fopen((basename + "_renderTiming.txt").c_str(), "w");
-    if (timing_file_ == NULL) {
+    if (timing_file_ == nullptr) {
       return -1;
     }
   }
-  if (out_file_ == NULL || video_frame.width() != width_ ||
+  if (out_file_ == nullptr || video_frame.width() != width_ ||
       video_frame.height() != height_) {
     if (out_file_) {
       fclose(out_file_);
@@ -120,7 +120,7 @@ int32_t FileOutputFrameReceiver::FrameToRender(webrtc::VideoFrame& video_frame,
         AppendWidthHeightCount(out_filename_, width_, height_, count_);
     ++count_;
     out_file_ = fopen(filename_with_width_height.c_str(), "wb");
-    if (out_file_ == NULL) {
+    if (out_file_ == nullptr) {
       return -1;
     }
   }