Replace NULL with nullptr in all C++ files.

webrtc/p2p/base/pseudotcp.cc

Index: webrtc/p2p/base/pseudotcp.cc
diff --git a/webrtc/p2p/base/pseudotcp.cc b/webrtc/p2p/base/pseudotcp.cc
index 8257b92c310e30d9ef11e0536d85351a68e84ae1..c6d95babfecfc6add7784683218b73ee96d7bcd4 100644
--- a/webrtc/p2p/base/pseudotcp.cc
+++ b/webrtc/p2p/base/pseudotcp.cc
@@ -426,7 +426,7 @@ int PseudoTcp::Recv(char* buffer, size_t len) {
   }
 
   size_t read = 0;
-  rtc::StreamResult result = m_rbuf.Read(buffer, len, &read, NULL);
+  rtc::StreamResult result = m_rbuf.Read(buffer, len, &read, nullptr);
 
   // If there's no data in |m_rbuf|.
   if (result == rtc::SR_BLOCK) {
@@ -508,7 +508,7 @@ uint32_t PseudoTcp::queue(const char* data, uint32_t len, bool bCtrl) {
   }
 
   size_t written = 0;
-  m_sbuf.Write(data, len, &written, NULL);
+  m_sbuf.Write(data, len, &written, nullptr);
   return static_cast<uint32_t>(written);
 }
 
@@ -909,7 +909,7 @@ bool PseudoTcp::process(Segment& seg) {
       uint32_t nOffset = seg.seq - m_rcv_nxt;
 
       rtc::StreamResult result =
-          m_rbuf.WriteOffset(seg.data, seg.len, nOffset, NULL);
+          m_rbuf.WriteOffset(seg.data, seg.len, nOffset, nullptr);
       if (result == rtc::SR_BLOCK) {
         // Ignore incoming packets outside of the receive window.
         return false;