Replace NULL with nullptr in all C++ files.

webrtc/p2p/base/p2ptransportchannel.cc

Index: webrtc/p2p/base/p2ptransportchannel.cc
diff --git a/webrtc/p2p/base/p2ptransportchannel.cc b/webrtc/p2p/base/p2ptransportchannel.cc
index 5bb6cf8aa4b20344e15b1786fc462ea08d3a568a..b77717c88adad080f0ed7343caef056b13d28cc0 100644
--- a/webrtc/p2p/base/p2ptransportchannel.cc
+++ b/webrtc/p2p/base/p2ptransportchannel.cc
@@ -789,7 +789,7 @@ void P2PTransportChannel::AddRemoteCandidate(const Candidate& candidate) {
   }
 
   // Create connections to this remote candidate.
-  CreateConnections(new_remote_candidate, NULL);
+  CreateConnections(new_remote_candidate, nullptr);
 
   // Resort the connections list, which may have new elements.
   SortConnectionsAndUpdateState();
@@ -822,7 +822,7 @@ bool P2PTransportChannel::CreateConnections(const Candidate& remote_candidate,
   // re-create any connections that were previously pruned, which will then
   // immediately be re-pruned, churning the network for no purpose.
   // This only applies to candidates received over signaling (i.e. origin_port
-  // is NULL).
+  // is null).
   if (!origin_port && IsDuplicateRemoteCandidate(remote_candidate)) {
     // return true to indicate success, without creating any new connections.
     return true;
@@ -842,7 +842,7 @@ bool P2PTransportChannel::CreateConnections(const Candidate& remote_candidate,
     }
   }
 
-  if ((origin_port != NULL) &&
+  if ((origin_port != nullptr) &&
       std::find(ports_.begin(), ports_.end(), origin_port) == ports_.end()) {
     if (CreateConnection(origin_port, remote_candidate, origin_port))
       created = true;
@@ -1369,7 +1369,7 @@ void P2PTransportChannel::PruneConnections() {
 
 // Change the selected connection, and let listeners know.
 void P2PTransportChannel::SwitchSelectedConnection(Connection* conn) {
-  // Note: if conn is NULL, the previous |selected_connection_| has been
+  // Note: if conn is null, the previous |selected_connection_| has been
   // destroyed, so don't use it.
   Connection* old_selected_connection = selected_connection_;
   selected_connection_ = conn;