Replace NULL with nullptr in all C++ files.

webrtc/video/video_receive_stream.cc

Index: webrtc/video/video_receive_stream.cc
diff --git a/webrtc/video/video_receive_stream.cc b/webrtc/video/video_receive_stream.cc
index 50c47e5a06b960af25140fc36b3143ec7f4958a8..1b50cbf65f15a6c08c781012a906f6abcbe7eab7 100644
--- a/webrtc/video/video_receive_stream.cc
+++ b/webrtc/video/video_receive_stream.cc
@@ -39,7 +39,7 @@ namespace webrtc {
 
 std::string VideoReceiveStream::Decoder::ToString() const {
   std::stringstream ss;
-  ss << "{decoder: " << (decoder ? "(VideoDecoder)" : "nullptr");
+  ss << "{decoder: " << (decoder ? "(VideoDecoder)" : "null");
   ss << ", payload_type: " << payload_type;
   ss << ", payload_name: " << payload_name;
   ss << ", codec_params: {";
@@ -61,12 +61,12 @@ std::string VideoReceiveStream::Config::ToString() const {
   }
   ss << ']';
   ss << ", rtp: " << rtp.ToString();
-  ss << ", renderer: " << (renderer ? "(renderer)" : "nullptr");
+  ss << ", renderer: " << (renderer ? "(renderer)" : "null");
   ss << ", render_delay_ms: " << render_delay_ms;
   if (!sync_group.empty())
     ss << ", sync_group: " << sync_group;
   ss << ", pre_decode_callback: "
-     << (pre_decode_callback ? "(EncodedFrameObserver)" : "nullptr");
+     << (pre_decode_callback ? "(EncodedFrameObserver)" : "null");
   ss << ", target_delay_ms: " << target_delay_ms;
   ss << '}';