Replace NULL with nullptr in all C++ files.

webrtc/pc/test/androidtestinitializer.cc

 /*
  *  Copyright 2015 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 21 matching lines @@
 namespace {
 
 static pthread_once_t g_initialize_once = PTHREAD_ONCE_INIT;
 
 // There can only be one JNI_OnLoad in each binary. So since this is a GTEST
 // C++ runner binary, we want to initialize the same global objects we normally
 // do if this had been a Java binary.
 void EnsureInitializedOnce() {
   RTC_CHECK(::base::android::IsVMInitialized());
   JNIEnv* jni = ::base::android::AttachCurrentThread();
-  JavaVM* jvm = NULL;
+  JavaVM* jvm = nullptr;
   RTC_CHECK_EQ(0, jni->GetJavaVM(&jvm));
   jobject context = ::base::android::GetApplicationContext().obj();
 
   RTC_CHECK(rtc::InitializeSSL()) << "Failed to InitializeSSL()";
 
   webrtc::VoiceEngine::SetAndroidObjects(jvm, context);
 }
 
 }  // anonymous namespace
 
 void InitializeAndroidObjects() {
   RTC_CHECK_EQ(0, pthread_once(&g_initialize_once, &EnsureInitializedOnce));
 }
 
 }  // namespace webrtc