Replace NULL with nullptr in all C++ files.

webrtc/modules/remote_bitrate_estimator/tools/rtp_to_text.cc

Index: webrtc/modules/remote_bitrate_estimator/tools/rtp_to_text.cc
diff --git a/webrtc/modules/remote_bitrate_estimator/tools/rtp_to_text.cc b/webrtc/modules/remote_bitrate_estimator/tools/rtp_to_text.cc
index 2b8c5b056c601f72a1d531c611976da14f1bc20e..ffb45c036a84e3707e5b64e5396704449a9a7839 100644
--- a/webrtc/modules/remote_bitrate_estimator/tools/rtp_to_text.cc
+++ b/webrtc/modules/remote_bitrate_estimator/tools/rtp_to_text.cc
@@ -22,8 +22,8 @@
 int main(int argc, char** argv) {
   webrtc::test::RtpFileReader* reader;
   webrtc::RtpHeaderParser* parser;
-  if (!ParseArgsAndSetupEstimator(argc, argv, NULL, NULL, &reader, &parser,
-                                  NULL, NULL)) {
+  if (!ParseArgsAndSetupEstimator(argc, argv, nullptr, nullptr, &reader,
+                                  &parser, nullptr, nullptr)) {
     return -1;
   }
   bool arrival_time_only = (argc >= 5 && strncmp(argv[4], "-t", 2) == 0);