Replace NULL with nullptr in all C++ files.

webrtc/modules/video_coding/generic_decoder.cc

Index: webrtc/modules/video_coding/generic_decoder.cc
diff --git a/webrtc/modules/video_coding/generic_decoder.cc b/webrtc/modules/video_coding/generic_decoder.cc
index 34500c69e2a39f9b69b0e2488318ce75ee0e370f..a0bdc4d5b279bf87d97477cb71ed455bcdafbe3b 100644
--- a/webrtc/modules/video_coding/generic_decoder.cc
+++ b/webrtc/modules/video_coding/generic_decoder.cc
@@ -22,7 +22,7 @@ VCMDecodedFrameCallback::VCMDecodedFrameCallback(VCMTiming* timing,
                                                  Clock* clock)
     : _critSect(CriticalSectionWrapper::CreateCriticalSection()),
       _clock(clock),
-      _receiveCallback(NULL),
+      _receiveCallback(nullptr),
       _timing(timing),
       _timestampMap(kDecoderFrameMemoryLength),
       _lastReceivedPictureID(0) {}
@@ -70,7 +70,7 @@ void VCMDecodedFrameCallback::Decoded(VideoFrame& decodedImage,
     callback = _receiveCallback;
   }
 
-  if (frameInfo == NULL) {
+  if (frameInfo == nullptr) {
     LOG(LS_WARNING) << "Too many frames backed up in the decoder, dropping "
                        "this one.";
     return;
@@ -87,7 +87,7 @@ void VCMDecodedFrameCallback::Decoded(VideoFrame& decodedImage,
   decodedImage.set_timestamp_us(
       frameInfo->renderTimeMs * rtc::kNumMicrosecsPerMillisec);
   decodedImage.set_rotation(frameInfo->rotation);
-  // TODO(sakal): Investigate why callback is NULL sometimes and replace if
+  // TODO(sakal): Investigate why callback is null sometimes and replace if
   // statement with a DCHECK.
   if (callback) {
     callback->FrameToRender(decodedImage, qp);
@@ -99,7 +99,7 @@ void VCMDecodedFrameCallback::Decoded(VideoFrame& decodedImage,
 int32_t VCMDecodedFrameCallback::ReceivedDecodedReferenceFrame(
     const uint64_t pictureId) {
   CriticalSectionScoped cs(_critSect);
-  if (_receiveCallback != NULL) {
+  if (_receiveCallback != nullptr) {
     return _receiveCallback->ReceivedDecodedReferenceFrame(pictureId);
   }
   return -1;
@@ -130,14 +130,14 @@ void VCMDecodedFrameCallback::Map(uint32_t timestamp,
 
 int32_t VCMDecodedFrameCallback::Pop(uint32_t timestamp) {
   CriticalSectionScoped cs(_critSect);
-  if (_timestampMap.Pop(timestamp) == NULL) {
+  if (_timestampMap.Pop(timestamp) == nullptr) {
     return VCM_GENERAL_ERROR;
   }
   return VCM_OK;
 }
 
 VCMGenericDecoder::VCMGenericDecoder(VideoDecoder* decoder, bool isExternal)
-    : _callback(NULL),
+    : _callback(nullptr),
       _frameInfos(),
       _nextFrameInfoIdx(0),
       _decoder(decoder),