Test refactors to allow for delaying response trailers.

net/quic/test_tools/quic_session_peer.cc

Index: net/quic/test_tools/quic_session_peer.cc
diff --git a/net/quic/test_tools/quic_session_peer.cc b/net/quic/test_tools/quic_session_peer.cc
index b4d49f768b9728bfc581c14ed56b7e13e2906a4c..a6f8c8365369f7bbf6f0b62bbb518e1e78c02205 100644
--- a/net/quic/test_tools/quic_session_peer.cc
+++ b/net/quic/test_tools/quic_session_peer.cc
@@ -67,6 +67,12 @@ QuicSession::StaticStreamMap& QuicSessionPeer::static_streams(
 }
 
 // static
+QuicSession::DynamicStreamMap& QuicSessionPeer::dynamic_streams(
+    QuicSession* session) {
+  return session->dynamic_streams();
+}
+
+// static
 std::unordered_set<QuicStreamId>* QuicSessionPeer::GetDrainingStreams(
     QuicSession* session) {
   return &session->draining_streams_;