Add ActivateStream() to QuicSessionPeer.

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 a2d624777a9a15fc2bf254fa8bce58eb0a28bebc..14c147552977dc09167a2a9cdd05959cd09f535e 100644
--- a/net/quic/test_tools/quic_session_peer.cc
+++ b/net/quic/test_tools/quic_session_peer.cc
@@ -72,6 +72,12 @@ std::unordered_set<QuicStreamId>* QuicSessionPeer::GetDrainingStreams(
 }
 
 // static
+void QuicSessionPeer::ActivateStream(QuicSession* session,
+                                     ReliableQuicStream* stream) {
+  return session->ActivateStream(stream);
+}
+
+// static
 bool QuicSessionPeer::IsStreamClosed(QuicSession* session, QuicStreamId id) {
   DCHECK_NE(0u, id);
   return session->IsClosedStream(id);