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 66df339efe05f050d2cabbd955c9694917019588..26de30ec3182cf6d7752a0b6e9949d8c611982df 100644
--- a/webrtc/video/rtp_video_stream_receiver.cc
+++ b/webrtc/video/rtp_video_stream_receiver.cc
@@ -558,7 +558,6 @@ 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;