Replace NULL with nullptr in all C++ files.

webrtc/modules/video_coding/test/vcm_payload_sink_factory.cc

Index: webrtc/modules/video_coding/test/vcm_payload_sink_factory.cc
diff --git a/webrtc/modules/video_coding/test/vcm_payload_sink_factory.cc b/webrtc/modules/video_coding/test/vcm_payload_sink_factory.cc
index 5604e62893d33d2fcb0ddf09878b9f0f4b752cc8..6c0ab860db81fc1aaa1cfd9a679e935066d5a6ee 100644
--- a/webrtc/modules/video_coding/test/vcm_payload_sink_factory.cc
+++ b/webrtc/modules/video_coding/test/vcm_payload_sink_factory.cc
@@ -127,8 +127,8 @@ PayloadSinkInterface* VcmPayloadSinkFactory::Create(
 
   std::unique_ptr<VideoCodingModule> vcm(
       VideoCodingModule::Create(clock_, null_event_factory_.get()));
-  if (vcm.get() == NULL) {
-    return NULL;
+  if (vcm.get() == nullptr) {
+    return nullptr;
   }
 
   const PayloadTypes& plt = stream->payload_types();
@@ -139,7 +139,7 @@ PayloadSinkInterface* VcmPayloadSinkFactory::Create(
       VideoCodingModule::Codec(it->codec_type(), &codec);
       codec.plType = it->payload_type();
       if (vcm->RegisterReceiveCodec(&codec, 1) < 0) {
-        return NULL;
+        return nullptr;
       }
     }
   }