Write a buffer's meta data into QUIC

Summary:
Instead of writing real data into the transport, we want to support a
use case where only its metadata is written to the transport. Sending of the
real data is delegated to another entity in such setup.

Reviewed By: mjoras

Differential Revision: D26131772

fbshipit-source-id: 4fcfa3a1626203f63c61898e6de089a3079d043d

quic/state/QuicStreamFunctions.h

@@ -21,6 +21,17 @@ namespace quic {
  */
 void writeDataToQuicStream(QuicStreamState& stream, Buf data, bool eof);
 
+/**
+ * Adds data represented in the form of BufferMeta to the end of the Buffer
+ * Meta queue of the stream.
+ *
+ * TODO: move to dsr directory.
+ */
+void writeBufMetaToQuicStream(
+    QuicStreamState& stream,
+    const BufferMeta& data,
+    bool eof);
+
 /**
  * Adds data to the end of the write buffer of the QUIC crypto stream. This
  * data will be written onto the socket.