Adds missing include.

net/quic/quartc/quartc_factory.h

 // Copyright (c) 2017 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.
 
 #ifndef NET_QUIC_QUARTC_QUARTC_FACTORY_H_
 #define NET_QUIC_QUARTC_QUARTC_FACTORY_H_
 
 #include "net/quic/core/quic_alarm_factory.h"
 #include "net/quic/core/quic_connection.h"
 #include "net/quic/core/quic_simple_buffer_allocator.h"
+#include "net/quic/platform/api/quic_export.h"
 #include "net/quic/quartc/quartc_factory_interface.h"
 #include "net/quic/quartc/quartc_packet_writer.h"
 #include "net/quic/quartc/quartc_task_runner_interface.h"
 
 namespace net {
 
 // Implements the QuartcFactoryInterface to create the instances of
 // QuartcSessionInterface. Implements the QuicAlarmFactory to create alarms
 // using the QuartcTaskRunner. Implements the QuicConnectionHelperInterface used
 // by the QuicConnections. Only one QuartcFactory is expected to be created.
@@ skipping 32 matching lines @@
   // Used to implement the QuicConnectionHelperInterface.
   // The QuicClock wrapper held in this variable is owned by QuartcFactory,
   // but the QuartcClockInterface inside of it belongs to the user!
   std::unique_ptr<QuicClock> clock_;
   SimpleBufferAllocator buffer_allocator_;
 };
 
 }  // namespace net
 
 #endif  // NET_QUIC_QUARTC_QUARTC_FACTORY_H_