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

net/quic/core/crypto/crypto_server_test.cc

 // Copyright (c) 2013 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 <algorithm>
 #include <cstdint>
 #include <memory>
 #include <ostream>
 #include <vector>
 
@@ skipping 344 matching lines @@
            GetParam().use_stateless_rejects;
   }
 
   string XlctHexString() {
     uint64_t xlct = CryptoTestUtils::LeafCertHashForTesting();
     return "#" +
            QuicUtils::HexEncode(reinterpret_cast<char*>(&xlct), sizeof(xlct));
   }
 
  protected:
+  QuicFlagSaver flags_;  // Save/restore all QUIC flag values.
   QuicRandom* const rand_;
   MockRandom rand_for_id_generation_;
   MockClock clock_;
   IPEndPoint client_address_;
   QuicVersionVector supported_versions_;
   QuicVersion client_version_;
   string client_version_string_;
   QuicCryptoServerConfig config_;
   QuicCompressedCertsCache compressed_certs_cache_;
   QuicCryptoServerConfig::ConfigOptions config_options_;
@@ skipping 868 matching lines @@
     EXPECT_EQ(0, strike_register_client_->PendingVerifications());
   } else {
     // version 33.
     ASSERT_EQ(kSHLO, out_.tag());
     CheckServerHello(out_);
   }
 }
 
 }  // namespace test
 }  // namespace net