Replace NULL with nullptr in all C++ files.

webrtc/voice_engine/test/auto_test/fixtures/before_initialization_fixture.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.
  */
 
 #include "webrtc/voice_engine/test/auto_test/fixtures/before_initialization_fixture.h"
 
 #include "webrtc/system_wrappers/include/sleep.h"
 
 BeforeInitializationFixture::BeforeInitializationFixture()
     : voice_engine_(webrtc::VoiceEngine::Create()) {
-  EXPECT_TRUE(voice_engine_ != NULL);
+  EXPECT_TRUE(voice_engine_ != nullptr);
 
   voe_base_ = webrtc::VoEBase::GetInterface(voice_engine_);
   voe_codec_ = webrtc::VoECodec::GetInterface(voice_engine_);
   voe_volume_control_ = webrtc::VoEVolumeControl::GetInterface(voice_engine_);
   voe_rtp_rtcp_ = webrtc::VoERTP_RTCP::GetInterface(voice_engine_);
   voe_apm_ = webrtc::VoEAudioProcessing::GetInterface(voice_engine_);
   voe_network_ = webrtc::VoENetwork::GetInterface(voice_engine_);
   voe_file_ = webrtc::VoEFile::GetInterface(voice_engine_);
   voe_vsync_ = webrtc::VoEVideoSync::GetInterface(voice_engine_);
   voe_hardware_ = webrtc::VoEHardware::GetInterface(voice_engine_);
@@ skipping 13 matching lines @@
   voe_hardware_->Release();
   voe_xmedia_->Release();
   voe_neteq_stats_->Release();
 
   EXPECT_TRUE(webrtc::VoiceEngine::Delete(voice_engine_));
 }
 
 void BeforeInitializationFixture::Sleep(long milliseconds) {
   webrtc::SleepMs(milliseconds);
 }