Replace NULL with nullptr in all C++ files.

webrtc/modules/audio_coding/test/TestRedFec.cc

Index: webrtc/modules/audio_coding/test/TestRedFec.cc
diff --git a/webrtc/modules/audio_coding/test/TestRedFec.cc b/webrtc/modules/audio_coding/test/TestRedFec.cc
index 7877204890eaa9b8c05aba4c1bbcd3097d45d5e6..c13291a23aada16debb0d94065451da3785dae0c 100644
--- a/webrtc/modules/audio_coding/test/TestRedFec.cc
+++ b/webrtc/modules/audio_coding/test/TestRedFec.cc
@@ -51,14 +51,13 @@ namespace {
 TestRedFec::TestRedFec()
     : _acmA(AudioCodingModule::Create(0)),
       _acmB(AudioCodingModule::Create(1)),
-      _channelA2B(NULL),
-      _testCntr(0) {
-}
+      _channelA2B(nullptr),
+      _testCntr(0) {}
 
 TestRedFec::~TestRedFec() {
-  if (_channelA2B != NULL) {
+  if (_channelA2B != nullptr) {
     delete _channelA2B;
-    _channelA2B = NULL;
+    _channelA2B = nullptr;
   }
 }
 
@@ -438,7 +437,7 @@ int16_t TestRedFec::RegisterSendCodec(char side, const char* codecName,
       return -1;
   }
 
-  if (myACM == NULL) {
+  if (myACM == nullptr) {
     assert(false);
     return -1;
   }