Fix two TSAN bugs exposed when running with -c opt:

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 1350 matching lines @@
     case kTBBR:
       expected_congestion_control_type = kBBR;
       break;
     case kQBIC:
       expected_congestion_control_type = kCubic;
       break;
     default:
       DLOG(FATAL) << "Unexpected congestion control tag";
   }
 
+  server_thread_->Pause();
   EXPECT_EQ(expected_congestion_control_type,
             QuicSentPacketManagerPeer::GetSendAlgorithm(
                 *static_cast<const QuicSentPacketManager*>(
                     GetSentPacketManagerFromFirstServerSession()))
                 ->GetCongestionControlType());
+  server_thread_->Resume();
 }
 
 TEST_P(EndToEndTest, LimitMaxOpenStreams) {
   // Server limits the number of max streams to 2.
   server_config_.SetMaxStreamsPerConnection(2, 2);
   // Client tries to negotiate for 10.
   client_config_.SetMaxStreamsPerConnection(10, 5);
 
   ASSERT_TRUE(Initialize());
   client_->client()->WaitForCryptoHandshakeConfirmed();
@@ skipping 1535 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