Report interframe delay sum in old GetStats

webrtc/video_receive_stream.h

Index: webrtc/video_receive_stream.h
diff --git a/webrtc/video_receive_stream.h b/webrtc/video_receive_stream.h
index b3a98c617ac2ebc120bf50f557faf537af47ba52..0d6aa9361c6f5f9179aed4e052c825fec0d8a716 100644
--- a/webrtc/video_receive_stream.h
+++ b/webrtc/video_receive_stream.h
@@ -69,6 +69,7 @@ class VideoReceiveStream {
     int jitter_buffer_ms = 0;
     int min_playout_delay_ms = 0;
     int render_delay_ms = 10;
+    uint64_t interframe_delay_sum_ms = 0;
     uint32_t frames_decoded = 0;
     rtc::Optional<uint64_t> qp_sum;