Move responsibility for RTP header extensions on video receive.

webrtc/call/flexfec_receive_stream.h

Index: webrtc/call/flexfec_receive_stream.h
diff --git a/webrtc/call/flexfec_receive_stream.h b/webrtc/call/flexfec_receive_stream.h
index babeee0ecb64c4c93d4c961c9c3adaeb100893fb..748f2b64ca8dc7efda3a41c5d595bdb0453a8bf9 100644
--- a/webrtc/call/flexfec_receive_stream.h
+++ b/webrtc/call/flexfec_receive_stream.h
@@ -68,9 +68,6 @@ class FlexfecReceiveStream {
     // |transport_cc| is true whenever the send-side BWE RTCP feedback message
     // has been negotiated. This is a prerequisite for enabling send-side BWE.
     bool transport_cc = false;
-
-    // RTP header extensions that have been negotiated for this track.
-    std::vector<RtpExtension> rtp_header_extensions;
   };
 
   // Starts stream activity.