Replace NULL with nullptr in all C++ files.

webrtc/pc/dtmfsender.cc

 /*
  *  Copyright 2012 The WebRTC project authors. All Rights Reserved.
  *
  *  Use of this source code is governed by a BSD-style license
  *  that can be found in the LICENSE file in the root of the source
  *  tree. An additional intellectual property rights grant can be found
  *  in the file PATENTS.  All contributing project authors may
  *  be found in the AUTHORS file in the root of the source tree.
  */
 
@@ skipping 58 matching lines @@
   rtc::scoped_refptr<DtmfSender> dtmf_sender(
       new rtc::RefCountedObject<DtmfSender>(track, signaling_thread,
                                                   provider));
   return dtmf_sender;
 }
 
 DtmfSender::DtmfSender(AudioTrackInterface* track,
                        rtc::Thread* signaling_thread,
                        DtmfProviderInterface* provider)
     : track_(track),
-      observer_(NULL),
+      observer_(nullptr),
       signaling_thread_(signaling_thread),
       provider_(provider),
       duration_(kDtmfDefaultDurationMs),
       inter_tone_gap_(kDtmfDefaultGapMs) {
-  RTC_DCHECK(signaling_thread_ != NULL);
+  RTC_DCHECK(signaling_thread_ != nullptr);
   // TODO(deadbeef): Once we can use shared_ptr and weak_ptr,
   // do that instead of relying on a "destroyed" signal.
   if (provider_) {
-    RTC_DCHECK(provider_->GetOnDestroyedSignal() != NULL);
+    RTC_DCHECK(provider_->GetOnDestroyedSignal() != nullptr);
     provider_->GetOnDestroyedSignal()->connect(
         this, &DtmfSender::OnProviderDestroyed);
   }
 }
 
 DtmfSender::~DtmfSender() {
   StopSending();
 }
 
 void DtmfSender::RegisterObserver(DtmfSenderObserverInterface* observer) {
   observer_ = observer;
 }
 
 void DtmfSender::UnregisterObserver() {
-  observer_ = NULL;
+  observer_ = nullptr;
 }
 
 bool DtmfSender::CanInsertDtmf() {
   RTC_DCHECK(signaling_thread_->IsCurrent());
   if (!provider_) {
     return false;
   }
   return provider_->CanInsertDtmf();
 }
 
@@ skipping 108 matching lines @@
   tones_.erase(0, first_tone_pos + 1);
 
   // Continue with the next tone.
   signaling_thread_->PostDelayed(RTC_FROM_HERE, tone_gap, this,
                                  MSG_DO_INSERT_DTMF);
 }
 
 void DtmfSender::OnProviderDestroyed() {
   LOG(LS_INFO) << "The Dtmf provider is deleted. Clear the sending queue.";
   StopSending();
-  provider_ = NULL;
+  provider_ = nullptr;
 }
 
 void DtmfSender::StopSending() {
   signaling_thread_->Clear(this);
 }
 
 }  // namespace webrtc