In QUIC, send data is copied to streams rather than frames. Protected by FLAGS_quic_reloadable_flag…

net/quic/test_tools/quic_stream_peer.cc

Index: net/quic/test_tools/quic_stream_peer.cc
diff --git a/net/quic/test_tools/quic_stream_peer.cc b/net/quic/test_tools/quic_stream_peer.cc
index 4dfbea7e3ac734e81fc0d5fe50e2cb7effdbd100..213be6621e461b8a8dcf7b34c6902d2589e760bd 100644
--- a/net/quic/test_tools/quic_stream_peer.cc
+++ b/net/quic/test_tools/quic_stream_peer.cc
@@ -81,5 +81,10 @@ QuicSession* QuicStreamPeer::session(QuicStream* stream) {
   return stream->session();
 }
 
+// static
+QuicStreamSendBuffer& QuicStreamPeer::SendBuffer(QuicStream* stream) {
+  return stream->send_buffer_;
+}
+
 }  // namespace test
 }  // namespace net