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

net/quic/core/quic_connection_test.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/core/quic_connection.h"
 
 #include <errno.h>
 #include <memory>
 #include <ostream>
 #include <utility>
@@ skipping 1044 matching lines @@
     EXPECT_CALL(*send_algorithm_, TimeUntilSend(_, _))
         .WillRepeatedly(testing::Return(QuicTime::Delta::Zero()));
   }
 
   void set_perspective(Perspective perspective) {
     connection_.set_perspective(perspective);
     QuicFramerPeer::SetPerspective(&peer_framer_,
                                    InvertPerspective(perspective));
   }
 
+  QuicFlagSaver flags_;  // Save/restore all QUIC flag values.
+
   QuicConnectionId connection_id_;
   QuicFramer framer_;
   MockEntropyCalculator entropy_calculator_;
   MockEntropyCalculator peer_entropy_calculator_;
 
   MockSendAlgorithm* send_algorithm_;
   std::unique_ptr<MockLossAlgorithm> loss_algorithm_;
   MockClock clock_;
   MockRandom random_generator_;
   SimpleBufferAllocator buffer_allocator_;
@@ skipping 3902 matching lines @@
               OnConnectionClosed(QUIC_ATTEMPT_TO_SEND_UNENCRYPTED_STREAM_DATA,
                                  _, ConnectionCloseSource::FROM_SELF));
   EXPECT_QUIC_BUG(connection_.SendStreamDataWithString(3, "", 0, kFin, nullptr),
                   "Cannot send stream data without encryption.");
   EXPECT_FALSE(connection_.connected());
 }
 
 TEST_P(QuicConnectionTest, EnableMultipathNegotiation) {
   // Test multipath negotiation during crypto handshake. Multipath is enabled
   // when both endpoints enable multipath.
-  ValueRestore<bool> old_flag(&FLAGS_quic_enable_multipath, true);
+  FLAGS_quic_enable_multipath = true;
   EXPECT_TRUE(connection_.connected());
   EXPECT_FALSE(QuicConnectionPeer::IsMultipathEnabled(&connection_));
   EXPECT_CALL(*send_algorithm_, SetFromConfig(_, _));
   QuicConfig config;
   // Enable multipath on server side.
   config.SetMultipathEnabled(true);
 
   // Create a handshake message enables multipath.
   CryptoHandshakeMessage msg;
   string error_details;
@@ skipping 207 matching lines @@
   connection_.SendStreamDataWithString(3, "foo", 0, !kFin, nullptr);
   EXPECT_EQ(1u, writer_->frame_count());
   EXPECT_FALSE(writer_->connection_close_frames().empty());
   // Ack frame is not bundled in connection close packet.
   EXPECT_TRUE(writer_->ack_frames().empty());
 }
 
 }  // namespace
 }  // namespace test
 }  // namespace net