Replace NULL with nullptr in all C++ files.

webrtc/modules/audio_processing/transient/transient_detector_unittest.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 68 matching lines @@
     const float kTolerance = 0.02f;
 
     size_t frames_read = 0;
 
     while (ReadInt16FromFileToFloatBuffer(audio_file.get(),
                                           buffer_length,
                                           buffer.get()) == buffer_length) {
       ++frames_read;
 
       float detector_value =
-          detector.Detect(buffer.get(), buffer_length, NULL, 0);
+          detector.Detect(buffer.get(), buffer_length, nullptr, 0);
       double file_value;
       ASSERT_EQ(1u, ReadDoubleBufferFromFile(detect_file.get(), 1, &file_value))
           << "Detect test file is malformed.\n";
 
       // Compare results with data from the matlab test file.
       EXPECT_NEAR(file_value, detector_value, kTolerance) << "Frame: "
           << frames_read;
     }
 
     detect_file->CloseFile();
     audio_file->CloseFile();
   }
 }
 
 }  // namespace webrtc