Add a flags field to video timing extension.

webrtc/video/rtp_video_stream_receiver.cc

Index: webrtc/video/rtp_video_stream_receiver.cc
diff --git a/webrtc/video/rtp_video_stream_receiver.cc b/webrtc/video/rtp_video_stream_receiver.cc
index d4464ac21dd568d29b249d282cee90fb19661185..6064e6971557932d3cd8ffea8bb6cf680ca68af4 100644
--- a/webrtc/video/rtp_video_stream_receiver.cc
+++ b/webrtc/video/rtp_video_stream_receiver.cc
@@ -560,7 +560,6 @@ void RtpVideoStreamReceiver::NotifyReceiverOfFecPacket(
   rtp_header.type.Video.video_timing = {0u, 0u, 0u, 0u, 0u, 0u, false};
   if (header.extension.has_video_timing) {
     rtp_header.type.Video.video_timing = header.extension.video_timing;
-    rtp_header.type.Video.video_timing.is_timing_frame = true;
   }
   rtp_header.type.Video.playout_delay = header.extension.playout_delay;