Replace NULL with nullptr in all C++ files.

webrtc/p2p/base/port.cc

Index: webrtc/p2p/base/port.cc
diff --git a/webrtc/p2p/base/port.cc b/webrtc/p2p/base/port.cc
index 385022c11aa98fd7be768c672617c5a900d5b5de..7058255690f0530638b57382945d68f2f4c9e4d3 100644
--- a/webrtc/p2p/base/port.cc
+++ b/webrtc/p2p/base/port.cc
@@ -185,7 +185,7 @@ Port::Port(rtc::Thread* thread,
       ice_role_(ICEROLE_UNKNOWN),
       tiebreaker_(0),
       shared_socket_(false) {
-  RTC_DCHECK(factory_ != NULL);
+  RTC_DCHECK(factory_ != nullptr);
   Construct();
 }
 
@@ -240,7 +240,7 @@ Connection* Port::GetConnection(const rtc::SocketAddress& remote_addr) {
   if (iter != connections_.end())
     return iter->second;
   else
-    return NULL;
+    return nullptr;
 }
 
 void Port::AddAddress(const rtc::SocketAddress& address,
@@ -356,8 +356,8 @@ bool Port::GetStunMessage(const char* data,
   // NOTE: This could clearly be optimized to avoid allocating any memory.
   //       However, at the data rates we'll be looking at on the client side,
   //       this probably isn't worth worrying about.
-  RTC_DCHECK(out_msg != NULL);
-  RTC_DCHECK(out_username != NULL);
+  RTC_DCHECK(out_msg != nullptr);
+  RTC_DCHECK(out_username != nullptr);
   out_username->clear();
 
   // Don't bother parsing the packet if we can tell it's not STUN.
@@ -469,7 +469,7 @@ bool Port::ParseStunUsername(const StunMessage* stun_msg,
   remote_ufrag->clear();
   const StunByteStringAttribute* username_attr =
         stun_msg->GetByteString(STUN_ATTR_USERNAME);
-  if (username_attr == NULL)
+  if (username_attr == nullptr)
     return false;
 
   // RFRAG:LFRAG
@@ -560,8 +560,8 @@ void Port::SendBindingResponse(StunMessage* request,
   // Retrieve the username from the request.
   const StunByteStringAttribute* username_attr =
       request->GetByteString(STUN_ATTR_USERNAME);
-  RTC_DCHECK(username_attr != NULL);
-  if (username_attr == NULL) {
+  RTC_DCHECK(username_attr != nullptr);
+  if (username_attr == nullptr) {
     // No valid username, skip the response.
     return;
   }