Replace NULL with nullptr in all C++ files.

webrtc/modules/remote_bitrate_estimator/test/estimators/send_side.cc

 /*
  *  Copyright (c) 2015 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 134 matching lines @@
   packet_feedback_vector_.push_back(PacketInfo(
       -1, arrival_time_ms, media_packet.sender_timestamp_ms(),
       media_packet.header().sequenceNumber, media_packet.payload_size(), true));
 
   // Log received packet information.
   BweReceiver::ReceivePacket(arrival_time_ms, media_packet);
 }
 
 FeedbackPacket* SendSideBweReceiver::GetFeedback(int64_t now_ms) {
   if (now_ms - last_feedback_ms_ < kFeedbackIntervalMs)
-    return NULL;
+    return nullptr;
   last_feedback_ms_ = now_ms;
   int64_t corrected_send_time_ms =
       packet_feedback_vector_.back().send_time_ms + now_ms -
       packet_feedback_vector_.back().arrival_time_ms;
   FeedbackPacket* fb = new SendSideBweFeedback(
       flow_id_, now_ms * 1000, corrected_send_time_ms, packet_feedback_vector_);
   packet_feedback_vector_.clear();
   return fb;
 }
 
 }  // namespace bwe
 }  // namespace testing
 }  // namespace webrtc