Replace NULL with nullptr in webrtc/video.

webrtc/video/vie_remb.cc

 /*
  *  Copyright (c) 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 74 matching lines @@
   }
 }
 
 bool VieRemb::InUse() const {
   rtc::CritScope lock(&list_crit_);
   return !receive_modules_.empty() || !rtcp_sender_.empty();
 }
 
 void VieRemb::OnReceiveBitrateChanged(const std::vector<uint32_t>& ssrcs,
                                       uint32_t bitrate) {
-  RtpRtcp* sender = NULL;
+  RtpRtcp* sender = nullptr;
   {
     rtc::CritScope lock(&list_crit_);
     // If we already have an estimate, check if the new total estimate is below
     // kSendThresholdPercent of the previous estimate.
     if (last_send_bitrate_ > 0) {
       uint32_t new_remb_bitrate = last_send_bitrate_ - bitrate_ + bitrate;
 
       if (new_remb_bitrate < kSendThresholdPercent * last_send_bitrate_ / 100) {
         // The new bitrate estimate is less than kSendThresholdPercent % of the
         // last report. Send a REMB asap.
@@ skipping 22 matching lines @@
     }
     last_send_bitrate_ = bitrate_;
   }
 
   if (sender) {
     sender->SetREMBData(bitrate_, ssrcs);
   }
 }
 
 }  // namespace webrtc