Replace NULL with nullptr in all C++ files.

webrtc/modules/rtp_rtcp/source/rtp_rtcp_impl.cc

Index: webrtc/modules/rtp_rtcp/source/rtp_rtcp_impl.cc
diff --git a/webrtc/modules/rtp_rtcp/source/rtp_rtcp_impl.cc b/webrtc/modules/rtp_rtcp/source/rtp_rtcp_impl.cc
index 50885f457f2d9838a02682c653ae42c943cdc028..de02560df69eb4fd107f07b58ac9f3e071c5f6fa 100644
--- a/webrtc/modules/rtp_rtcp/source/rtp_rtcp_impl.cc
+++ b/webrtc/modules/rtp_rtcp/source/rtp_rtcp_impl.cc
@@ -159,7 +159,7 @@ void ModuleRtpRtcpImpl::Process() {
       for (std::vector<RTCPReportBlock>::iterator it = receive_blocks.begin();
            it != receive_blocks.end(); ++it) {
         int64_t rtt = 0;
-        rtcp_receiver_.RTT(it->remoteSSRC, &rtt, NULL, NULL, NULL);
+        rtcp_receiver_.RTT(it->remoteSSRC, &rtt, nullptr, nullptr, nullptr);
         max_rtt = (rtt > max_rtt) ? rtt : max_rtt;
       }
       // Report the rtt.
@@ -562,7 +562,7 @@ void ModuleRtpRtcpImpl::GetRtpPacketLossStats(
     uint32_t ssrc,
     struct RtpPacketLossStats* loss_stats) const {
   if (!loss_stats) return;
-  const PacketLossStats* stats_source = NULL;
+  const PacketLossStats* stats_source = nullptr;
   if (outgoing) {
     if (SSRC() == ssrc) {
       stats_source = &send_loss_stats_;
@@ -699,7 +699,8 @@ bool ModuleRtpRtcpImpl::TimeToSendFullNackList(int64_t now) const {
   // Use RTT from RtcpRttStats class if provided.
   int64_t rtt = rtt_ms();
   if (rtt == 0) {
-    rtcp_receiver_.RTT(rtcp_receiver_.RemoteSSRC(), NULL, &rtt, NULL, NULL);
+    rtcp_receiver_.RTT(rtcp_receiver_.RemoteSSRC(), nullptr, &rtt, nullptr,
+                       nullptr);
   }
 
   const int64_t kStartUpRttMs = 100;
@@ -843,7 +844,8 @@ void ModuleRtpRtcpImpl::OnReceivedNack(
   // Use RTT from RtcpRttStats class if provided.
   int64_t rtt = rtt_ms();
   if (rtt == 0) {
-    rtcp_receiver_.RTT(rtcp_receiver_.RemoteSSRC(), NULL, &rtt, NULL, NULL);
+    rtcp_receiver_.RTT(rtcp_receiver_.RemoteSSRC(), nullptr, &rtt, nullptr,
+                       nullptr);
   }
   rtp_sender_.OnReceivedNack(nack_sequence_numbers, rtt);
 }
@@ -861,11 +863,8 @@ bool ModuleRtpRtcpImpl::LastReceivedNTP(
   uint32_t ntp_secs = 0;
   uint32_t ntp_frac = 0;
 
-  if (!rtcp_receiver_.NTP(&ntp_secs,
-                          &ntp_frac,
-                          rtcp_arrival_time_secs,
-                          rtcp_arrival_time_frac,
-                          NULL)) {
+  if (!rtcp_receiver_.NTP(&ntp_secs, &ntp_frac, rtcp_arrival_time_secs,
+                          rtcp_arrival_time_frac, nullptr)) {
     return false;
   }
   *remote_sr =