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..610ac6bab30ccc18790f7ee8e2cbe45c582e63fd 100644
--- a/webrtc/modules/rtp_rtcp/source/rtp_packet.cc
+++ b/webrtc/modules/rtp_rtcp/source/rtp_packet.cc
@@ -169,6 +169,17 @@ void Packet::GetHeader(RTPHeader* header) const {
       &header->extension.voiceActivity, &header->extension.audioLevel);
   header->extension.hasVideoRotation =
       GetExtension<VideoOrientation>(&header->extension.videoRotation);
+  auto rsid = FindExtension(RtpStreamId::kId);
+  RTC_DCHECK_LE(rsid.size(), sizeof(header->extension.stream_id));
+  header->extension.stream_id_size = rsid.size();
+  memcpy(header->extension.stream_id, rsid.data(), rsid.size());
+
+  auto repaired_rsid = FindExtension(RepairedRtpStreamId::kId);
+  RTC_DCHECK_LE(repaired_rsid.size(),
+                sizeof(header->extension.repaired_stream_id));
+  header->extension.repaired_stream_id_size = repaired_rsid.size();
+  memcpy(header->extension.repaired_stream_id, repaired_rsid.data(),
+         repaired_rsid.size());
 }
 
 size_t Packet::headers_size() const {