Replace NULL with nullptr in all C++ files.

webrtc/modules/video_coding/codecs/tools/video_quality_measurement.cc

Index: webrtc/modules/video_coding/codecs/tools/video_quality_measurement.cc
diff --git a/webrtc/modules/video_coding/codecs/tools/video_quality_measurement.cc b/webrtc/modules/video_coding/codecs/tools/video_quality_measurement.cc
index f1b580719c0fd6e91d164d5998df11a3f5cc7692..2a925345a9c9fe07feef1d414af496f7e66cc638 100644
--- a/webrtc/modules/video_coding/codecs/tools/video_quality_measurement.cc
+++ b/webrtc/modules/video_coding/codecs/tools/video_quality_measurement.cc
@@ -155,7 +155,7 @@ int HandleCommandLineFlags(webrtc::test::TestConfig* config) {
   // Verify the input file exists and is readable.
   FILE* test_file;
   test_file = fopen(FLAGS_input_filename.c_str(), "rb");
-  if (test_file == NULL) {
+  if (test_file == nullptr) {
     fprintf(stderr, "Cannot read the specified input file: %s\n",
             FLAGS_input_filename.c_str());
     return 2;
@@ -194,7 +194,7 @@ int HandleCommandLineFlags(webrtc::test::TestConfig* config) {
     config->output_filename = FLAGS_output_dir + "/" + FLAGS_output_filename;
   }
   test_file = fopen(config->output_filename.c_str(), "wb");
-  if (test_file == NULL) {
+  if (test_file == nullptr) {
     fprintf(stderr, "Cannot write output file: %s\n",
             config->output_filename.c_str());
     return 4;
@@ -504,7 +504,7 @@ int main(int argc, char* argv[]) {
   // By default the packet manipulator is seeded with a fixed random.
   // If disabled we must generate a new seed.
   if (FLAGS_disable_fixed_random_seed) {
-    packet_manipulator.InitializeRandomSeed(time(NULL));
+    packet_manipulator.InitializeRandomSeed(time(nullptr));
   }
   webrtc::test::VideoProcessor* processor =
       new webrtc::test::VideoProcessorImpl(encoder, decoder, &frame_reader,