Fix net_export.h includes.

net/proxy/proxy_config_service_fixed.h

 // Copyright (c) 2011 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_PROXY_PROXY_CONFIG_SERVICE_FIXED_H_
 #define NET_PROXY_PROXY_CONFIG_SERVICE_FIXED_H_
 
 #include "base/compiler_specific.h"
 #include "net/base/net_errors.h"
+#include "net/base/net_export.h"
 #include "net/proxy/proxy_config.h"
 #include "net/proxy/proxy_config_service.h"
 
 namespace net {
 
 // Implementation of ProxyConfigService that returns a fixed result.
 class NET_EXPORT ProxyConfigServiceFixed : public ProxyConfigService {
  public:
   explicit ProxyConfigServiceFixed(const ProxyConfig& pc);
   ~ProxyConfigServiceFixed() override;
 
   // ProxyConfigService methods:
   void AddObserver(Observer* observer) override {}
   void RemoveObserver(Observer* observer) override {}
   ConfigAvailability GetLatestProxyConfig(ProxyConfig* config) override;
 
  private:
   ProxyConfig pc_;
 };
 
 }  // namespace net
 
 #endif  // NET_PROXY_PROXY_CONFIG_SERVICE_FIXED_H_