Replace NULL with nullptr in all C++ files.

webrtc/p2p/base/dtlstransportchannel.cc

Index: webrtc/p2p/base/dtlstransportchannel.cc
diff --git a/webrtc/p2p/base/dtlstransportchannel.cc b/webrtc/p2p/base/dtlstransportchannel.cc
index c4e1f5bcba63666ff17fa0c71b93ff9d4a508ce7..9bb6c68792ebdba838c0af54ff0b696f47e88428 100644
--- a/webrtc/p2p/base/dtlstransportchannel.cc
+++ b/webrtc/p2p/base/dtlstransportchannel.cc
@@ -95,7 +95,7 @@ rtc::StreamResult StreamInterfaceChannel::Write(const void* data,
 
 bool StreamInterfaceChannel::OnPacketReceived(const char* data, size_t size) {
   // We force a read event here to ensure that we don't overflow our queue.
-  bool ret = packets_.WriteBack(data, size, NULL);
+  bool ret = packets_.WriteBack(data, size, nullptr);
   RTC_CHECK(ret) << "Failed to write packet to queue.";
   if (ret) {
     SignalEvent(this, rtc::SE_READ, 0);
@@ -113,7 +113,7 @@ DtlsTransport::DtlsTransport(IceTransportInternal* ice_transport)
       component_(ice_transport->component()),
       network_thread_(rtc::Thread::Current()),
       ice_transport_(ice_transport),
-      downward_(NULL),
+      downward_(nullptr),
       ssl_role_(rtc::SSL_CLIENT),
       ssl_max_version_(rtc::SSL_PROTOCOL_DTLS_12) {
   ice_transport_->SignalWritableState.connect(this,
@@ -145,7 +145,7 @@ bool DtlsTransport::SetLocalCertificate(
     local_certificate_ = certificate;
     dtls_active_ = true;
   } else {
-    LOG_J(LS_INFO, this) << "NULL DTLS identity supplied. Not doing DTLS";
+    LOG_J(LS_INFO, this) << "null DTLS identity supplied. Not doing DTLS";
   }
 
   return true;
@@ -385,7 +385,7 @@ int DtlsTransport::SendPacket(const char* data,
   switch (dtls_state()) {
     case DTLS_TRANSPORT_NEW:
       // Can't send data until the connection is active.
-      // TODO(ekr@rtfm.com): assert here if dtls_ is NULL?
+      // TODO(ekr@rtfm.com): assert here if dtls_ is null?
       return -1;
     case DTLS_TRANSPORT_CONNECTING:
       // Can't send data until the connection is active.
@@ -399,7 +399,8 @@ int DtlsTransport::SendPacket(const char* data,
 
         return ice_transport_->SendPacket(data, size, options);
       } else {
-        return (dtls_->WriteAll(data, size, NULL, NULL) == rtc::SR_SUCCESS)
+        return (dtls_->WriteAll(data, size, nullptr, nullptr) ==
+                rtc::SR_SUCCESS)
                    ? static_cast<int>(size)
                    : -1;
       }