Replace NULL with nullptr in all C++ files.

webrtc/modules/audio_processing/transient/transient_detector.cc

 /*
  *  Copyright (c) 2013 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 128 matching lines @@
   // the previous results, so the high results have a width equals to
   // |transient_length|.
   return *std::max_element(previous_results_.begin(), previous_results_.end());
 }
 
 // Looks for the highest slope and compares it with the previous ones.
 // An exponential transformation takes this to the [0, 1] range. This value is
 // multiplied by the detection result to avoid false positives.
 float TransientDetector::ReferenceDetectionValue(const float* data,
                                                  size_t length) {
-  if (data == NULL) {
+  if (data == nullptr) {
     using_reference_ = false;
     return 1.f;
   }
   static const float kEnergyRatioThreshold = 0.2f;
   static const float kReferenceNonLinearity = 20.f;
   static const float kMemory = 0.99f;
   float reference_energy = 0.f;
   for (size_t i = 1; i < length; ++i) {
     reference_energy += data[i] * data[i];
   }
   if (reference_energy == 0.f) {
     using_reference_ = false;
     return 1.f;
   }
   RTC_DCHECK_NE(0, reference_energy_);
   float result = 1.f / (1.f + exp(kReferenceNonLinearity *
                                   (kEnergyRatioThreshold -
                                    reference_energy / reference_energy_)));
   reference_energy_ =
       kMemory * reference_energy_ + (1.f - kMemory) * reference_energy;
 
   using_reference_ = true;
 
   return result;
 }
 
 }  // namespace webrtc