Add read support of RtpStreamId/RepairedRtpStreamId header extensions.

webrtc/modules/rtp_rtcp/source/rtp_packet.cc

Index: webrtc/modules/rtp_rtcp/source/rtp_packet.cc
diff --git a/webrtc/modules/rtp_rtcp/source/rtp_packet.cc b/webrtc/modules/rtp_rtcp/source/rtp_packet.cc
index 0c28092d4c68a756eec3f67a4cefc4de8e23ed60..1d3afc44d1e5be82b142736ef5256ce255e4bd3e 100644
--- a/webrtc/modules/rtp_rtcp/source/rtp_packet.cc
+++ b/webrtc/modules/rtp_rtcp/source/rtp_packet.cc
@@ -169,6 +169,15 @@ void Packet::GetHeader(RTPHeader* header) const {
       &header->extension.voiceActivity, &header->extension.audioLevel);
   header->extension.hasVideoRotation =
       GetExtension<VideoOrientation>(&header->extension.videoRotation);
+  auto rid = FindExtension(RtpStreamId::kId);
+  RTC_DCHECK_LE(rid.size(), sizeof(header->extension.rid));
+  header->extension.rid_size = rid.size();
+  memcpy(header->extension.rid, rid.data(), rid.size());
+
+  auto repair_rid = FindExtension(RtpStreamId::kId);
+  RTC_DCHECK_LE(repair_rid.size(), sizeof(header->extension.repair_rid));
+  header->extension.repair_rid_size = repair_rid.size();
+  memcpy(header->extension.repair_rid, repair_rid.data(), repair_rid.size());
 }
 
 size_t Packet::headers_size() const {