Replace NULL with nullptr in all C++ files.

webrtc/voice_engine/test/auto_test/fixtures/after_initialization_fixture.cc

 /*
  *  Copyright (c) 2011 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/modules/audio_processing/include/audio_processing.h"
 #include "webrtc/voice_engine/test/auto_test/fixtures/after_initialization_fixture.h"
 
 class TestErrorObserver : public webrtc::VoiceEngineObserver {
  public:
   TestErrorObserver() {}
   virtual ~TestErrorObserver() {}
   void CallbackOnError(int channel, int error_code) {
     ADD_FAILURE() << "Unexpected error on channel " << channel <<
         ": error code " << error_code;
   }
 };
 
 AfterInitializationFixture::AfterInitializationFixture()
     : error_observer_(new TestErrorObserver()) {
   webrtc::Config config;
   config.Set<webrtc::ExperimentalAgc>(new webrtc::ExperimentalAgc(false));
   webrtc::AudioProcessing* audioproc = webrtc::AudioProcessing::Create(config);
 
-  EXPECT_EQ(0, voe_base_->Init(NULL, audioproc));
+  EXPECT_EQ(0, voe_base_->Init(nullptr, audioproc));
   EXPECT_EQ(0, voe_base_->RegisterVoiceEngineObserver(*error_observer_));
 }
 
 AfterInitializationFixture::~AfterInitializationFixture() {
   EXPECT_EQ(0, voe_base_->DeRegisterVoiceEngineObserver());
 }