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

net/tools/quic/end_to_end_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 <stddef.h>
 #include <sys/epoll.h>
 
 #include <list>
 #include <memory>
 #include <string>
@@ skipping 55 matching lines @@
 using net::test::CryptoTestUtils;
 using net::test::GenerateBody;
 using net::test::Loopback4;
 using net::test::MockQuicConnectionDebugVisitor;
 using net::test::QuicConnectionPeer;
 using net::test::QuicFlowControllerPeer;
 using net::test::QuicSentPacketManagerPeer;
 using net::test::QuicSessionPeer;
 using net::test::QuicSpdySessionPeer;
 using net::test::ReliableQuicStreamPeer;
-using net::test::ValueRestore;
 using net::test::kClientDataStreamId1;
 using net::test::kInitialSessionFlowControlWindowForTest;
 using net::test::kInitialStreamFlowControlWindowForTest;
 using net::test::PacketDroppingTestWriter;
 using net::test::QuicDispatcherPeer;
 using net::test::QuicServerPeer;
 using std::ostream;
 using std::string;
 using std::vector;
 
@@ skipping 1249 matching lines @@
   server_thread_->Pause();
   QuicDispatcher* dispatcher =
       QuicServerPeer::GetDispatcher(server_thread_->server());
   QuicSession* server_session = dispatcher->session_map().begin()->second;
   EXPECT_EQ(kClientMaxIncomingDynamicStreams,
             server_session->max_open_outgoing_streams());
   server_thread_->Resume();
 }
 
 TEST_P(EndToEndTest, NegotiateCongestionControl) {
-  ValueRestore<bool> old_flag(&FLAGS_quic_allow_bbr, true);
+  FLAGS_quic_allow_bbr = true;
   // Disable this flag because if connection uses multipath sent packet manager,
   // static_cast here does not work.
   FLAGS_quic_enable_multipath = false;
   ASSERT_TRUE(Initialize());
   client_->client()->WaitForCryptoHandshakeConfirmed();
 
   CongestionControlType expected_congestion_control_type = kReno;
   switch (GetParam().congestion_control_tag) {
     case kRENO:
       expected_congestion_control_type = kReno;
@@ skipping 1560 matching lines @@
   EXPECT_EQ(kBarResponseBody, client_->response_body());
   QuicConnectionStats client_stats =
       client_->client()->session()->connection()->GetStats();
   EXPECT_EQ(0u, client_stats.packets_lost);
   EXPECT_EQ(1, client_->client()->GetNumSentClientHellos());
 }
 
 }  // namespace
 }  // namespace test
 }  // namespace net