Add write support for the RtpStreamId and RepairedRtpStreamId header extensions.

webrtc/modules/rtp_rtcp/source/rtp_packet.h

Index: webrtc/modules/rtp_rtcp/source/rtp_packet.h
diff --git a/webrtc/modules/rtp_rtcp/source/rtp_packet.h b/webrtc/modules/rtp_rtcp/source/rtp_packet.h
index ca189dbe0d23bbe0c8f9da3dacf7649425aed235..029f215de0cc95437e563047e4e32b0f9db85fdd 100644
--- a/webrtc/modules/rtp_rtcp/source/rtp_packet.h
+++ b/webrtc/modules/rtp_rtcp/source/rtp_packet.h
@@ -183,7 +183,8 @@ bool Packet::GetExtension(Values... values) const {
 
 template <typename Extension, typename... Values>
 bool Packet::SetExtension(Values... values) {
-  auto buffer = AllocateExtension(Extension::kId, Extension::kValueSizeBytes);
+  auto buffer = AllocateExtension(Extension::kId,
+                                  Extension::ValueSize(values...));
   if (buffer.empty())
     return false;
   return Extension::Write(buffer.data(), values...);