Remove NullObjectReceiveStatistics() in rtp_rtcp module

webrtc/modules/rtp_rtcp/source/rtp_utility.cc

Index: webrtc/modules/rtp_rtcp/source/rtp_utility.cc
diff --git a/webrtc/modules/rtp_rtcp/source/rtp_utility.cc b/webrtc/modules/rtp_rtcp/source/rtp_utility.cc
index 9696ff4950a5f594f677193a7b3529e7710071df..4b5ecfa6983d61cba3ebaf9adc74496858c7f4bf 100644
--- a/webrtc/modules/rtp_rtcp/source/rtp_utility.cc
+++ b/webrtc/modules/rtp_rtcp/source/rtp_utility.cc
@@ -22,11 +22,6 @@ RtpFeedback* NullObjectRtpFeedback() {
   return &null_rtp_feedback;
 }
 
-ReceiveStatistics* NullObjectReceiveStatistics() {
-  static NullReceiveStatistics null_receive_statistics;
-  return &null_receive_statistics;
-}
-
 namespace RtpUtility {
 
 enum {