Replace NULL with nullptr in all C++ files.

webrtc/modules/audio_processing/transient/wpd_node_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 39 matching lines @@
   EXPECT_NEAR(0.1f, node.data()[0], kTolerance);
   EXPECT_NEAR(0.2f, node.data()[1], kTolerance);
   EXPECT_NEAR(0.18f, node.data()[2], kTolerance);
   EXPECT_NEAR(0.56f, node.data()[3], kTolerance);
   EXPECT_NEAR(0.94f, node.data()[4], kTolerance);
 }
 
 TEST(WPDNodeTest, ExpectedErrorReturnValue) {
   WPDNode node(kDataLength, kCoefficients, kCoefficientsLength);
   EXPECT_EQ(-1, node.Update(kParentData, kParentDataLength - 1));
-  EXPECT_EQ(-1, node.Update(NULL, kParentDataLength));
+  EXPECT_EQ(-1, node.Update(nullptr, kParentDataLength));
   EXPECT_EQ(-1, node.set_data(kParentData, kDataLength - 1));
-  EXPECT_EQ(-1, node.set_data(NULL, kDataLength));
+  EXPECT_EQ(-1, node.set_data(nullptr, kDataLength));
 }
 
 }  // namespace webrtc