Replace NULL with nullptr in all C++ files.

webrtc/base/socketaddress.cc

Index: webrtc/base/socketaddress.cc
diff --git a/webrtc/base/socketaddress.cc b/webrtc/base/socketaddress.cc
index 8cb53c5d57665f6d0c788640c1a08500ff016820..d931f72b21891a037d806d730cca5fc8b14c06c8 100644
--- a/webrtc/base/socketaddress.cc
+++ b/webrtc/base/socketaddress.cc
@@ -184,7 +184,7 @@ bool SocketAddress::FromString(const std::string& str) {
     if (closebracket != std::string::npos) {
       std::string::size_type colon = str.find(':', closebracket);
       if (colon != std::string::npos && colon > closebracket) {
-        SetPort(strtoul(str.substr(colon + 1).c_str(), NULL, 10));
+        SetPort(strtoul(str.substr(colon + 1).c_str(), nullptr, 10));
         SetIP(str.substr(1, closebracket - 1));
       } else {
         return false;
@@ -194,7 +194,7 @@ bool SocketAddress::FromString(const std::string& str) {
     std::string::size_type pos = str.find(':');
     if (std::string::npos == pos)
       return false;
-    SetPort(strtoul(str.substr(pos + 1).c_str(), NULL, 10));
+    SetPort(strtoul(str.substr(pos + 1).c_str(), nullptr, 10));
     SetIP(str.substr(0, pos));
   }
   return true;