Introduce MASQUE, part 2: client code

This CL introduces the client code for MASQUE as defined by <https://tools.ietf.org/html/draft-schinazi-masque>. Most of the work here is plumbing in order to override the right methods of the QUIC codebase. The meat of the MASQUE protocol work is in the parent cl/278956073.

gfe-relnote: n/a, adds unused code
PiperOrigin-RevId: 285443244
Change-Id: I76c66a4d89b8b70aada4f15f03ac5ec139ada22f
diff --git a/quic/masque/masque_encapsulated_epoll_client.h b/quic/masque/masque_encapsulated_epoll_client.h
new file mode 100644
index 0000000..c8bff21
--- /dev/null
+++ b/quic/masque/masque_encapsulated_epoll_client.h
@@ -0,0 +1,50 @@
+// Copyright 2019 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef QUICHE_QUIC_MASQUE_MASQUE_ENCAPSULATED_EPOLL_CLIENT_H_
+#define QUICHE_QUIC_MASQUE_MASQUE_ENCAPSULATED_EPOLL_CLIENT_H_
+
+#include "net/third_party/quiche/src/quic/masque/masque_encapsulated_client_session.h"
+#include "net/third_party/quiche/src/quic/masque/masque_epoll_client.h"
+#include "net/third_party/quiche/src/quic/platform/api/quic_export.h"
+#include "net/third_party/quiche/src/quic/tools/quic_client.h"
+
+namespace quic {
+
+// QUIC client for QUIC encapsulated in MASQUE.
+class QUIC_NO_EXPORT MasqueEncapsulatedEpollClient : public QuicClient {
+ public:
+  MasqueEncapsulatedEpollClient(QuicSocketAddress server_address,
+                                const QuicServerId& server_id,
+                                QuicEpollServer* epoll_server,
+                                std::unique_ptr<ProofVerifier> proof_verifier,
+                                MasqueEpollClient* masque_client);
+  ~MasqueEncapsulatedEpollClient() override;
+
+  // Disallow copy and assign.
+  MasqueEncapsulatedEpollClient(const MasqueEncapsulatedEpollClient&) = delete;
+  MasqueEncapsulatedEpollClient& operator=(
+      const MasqueEncapsulatedEpollClient&) = delete;
+
+  // From QuicClient.
+  std::unique_ptr<QuicSession> CreateQuicClientSession(
+      const ParsedQuicVersionVector& supported_versions,
+      QuicConnection* connection) override;
+
+  QuicConnectionId GetClientConnectionId() override;
+
+  // MASQUE client that this client is encapsulated in.
+  MasqueEpollClient* masque_client() { return masque_client_; }
+
+  // Client session for this client.
+  MasqueEncapsulatedClientSession* masque_encapsulated_client_session();
+
+ private:
+  MasqueEpollClient* masque_client_;  // Unowned.
+  QuicConnectionId client_connection_id_;
+};
+
+}  // namespace quic
+
+#endif  // QUICHE_QUIC_MASQUE_MASQUE_ENCAPSULATED_EPOLL_CLIENT_H_