Replace NULL with nullptr in all C++ files.

webrtc/modules/audio_processing/agc/loudness_histogram.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 156 matching lines @@
 double LoudnessHistogram::AudioContent() const {
   return audio_content_q10_ / kProbQDomain;
 }
 
 LoudnessHistogram* LoudnessHistogram::Create() {
   return new LoudnessHistogram;
 }
 
 LoudnessHistogram* LoudnessHistogram::Create(int window_size) {
   if (window_size < 0)
-    return NULL;
+    return nullptr;
   return new LoudnessHistogram(window_size);
 }
 
 void LoudnessHistogram::Reset() {
   // Reset the histogram, audio-content and number of updates.
   memset(bin_count_q10_, 0, sizeof(bin_count_q10_));
   audio_content_q10_ = 0;
   num_updates_ = 0;
   // Empty the circular buffer.
   buffer_index_ = 0;
@@ skipping 32 matching lines @@
       p = static_cast<double>(bin_count_q10_[n]) * p_total_inverse;
       mean_val += p * kHistBinCenters[n];
     }
   } else {
     mean_val = kHistBinCenters[0];
   }
   return mean_val;
 }
 
 }  // namespace webrtc