Add a new QuicFlagSaver class for saving/restoring the values of QUIC flags in tests.

net/quic/test_tools/quic_test_utils.cc

 // Copyright (c) 2012 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.
 
 #include "net/quic/test_tools/quic_test_utils.h"
 
 #include <memory>
 
 #include "base/sha1.h"
 #include "base/stl_util.h"
@@ skipping 79 matching lines @@
   DCHECK_NE(0u, length);
   // Re-construct the data packet with data ownership.
   return new QuicPacket(buffer, length, /* owns_buffer */ true,
                         header.public_header.connection_id_length,
                         header.public_header.version_flag,
                         header.public_header.multipath_flag,
                         header.public_header.nonce != nullptr,
                         header.public_header.packet_number_length);
 }
 
+QuicFlagSaver::QuicFlagSaver() {
+#define QUIC_FLAG(type, flag, value) CHECK_EQ(value, flag);
+#include "net/quic/core/quic_flags_list.h"
+#undef QUIC_FLAG
+}
+
+QuicFlagSaver::~QuicFlagSaver() {
+#define QUIC_FLAG(type, flag, value) flag = value;
+#include "net/quic/core/quic_flags_list.h"
+#undef QUIC_FLAG
+}
+
 uint64_t SimpleRandom::RandUint64() {
   unsigned char hash[base::kSHA1Length];
   base::SHA1HashBytes(reinterpret_cast<unsigned char*>(&seed_), sizeof(seed_),
                       hash);
   memcpy(&seed_, hash, sizeof(seed_));
   return seed_;
 }
 
 MockFramerVisitor::MockFramerVisitor() {
   // By default, we want to accept packets.
@@ skipping 790 matching lines @@
   // strike register worries that we've just overflowed a uint32_t time.
   (*server_connection)->AdvanceTime(connection_start_time);
 }
 
 QuicStreamId QuicClientDataStreamId(int i) {
   return kClientDataStreamId1 + 2 * i;
 }
 
 }  // namespace test
 }  // namespace net