Adds missing include.

net/quic/quartc/quartc_packet_writer.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_PACKET_WRITER_H_
 #define NET_QUIC_QUARTC_QUARTC_PACKET_WRITER_H_
 
 #include "net/quic/core/quic_packet_writer.h"
+#include "net/quic/platform/api/quic_export.h"
 #include "net/quic/quartc/quartc_session_interface.h"
 
 namespace net {
 
 // Implements a QuicPacketWriter using a
 // QuartcSessionInterface::PacketTransport, which allows a QuicConnection to
 // use(for example), a WebRTC IceTransport.
 class QUIC_EXPORT_PRIVATE QuartcPacketWriter : public QuicPacketWriter {
  public:
   QuartcPacketWriter(QuartcSessionInterface::PacketTransport* packet_transport,
@@ skipping 29 matching lines @@
  private:
   // QuartcPacketWriter will not own the transport.
   QuartcSessionInterface::PacketTransport* packet_transport_;
   // The maximum size of the packet can be written by this writer.
   QuicByteCount max_packet_size_;
 };
 
 }  // namespace net
 
 #endif  // NET_QUIC_QUARTC_QUARTC_PACKET_WRITER_H_