Convert FILE thread usage in system_network_api.cc to TaskScheduler.

extensions/browser/api/system_network/system_network_api.h

 // Copyright 2013 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 EXTENSIONS_BROWSER_API_SYSTEM_NETWORK_SYSTEM_NETWORK_API_H_
 #define EXTENSIONS_BROWSER_API_SYSTEM_NETWORK_SYSTEM_NETWORK_API_H_
 
+#include <memory>
+
 #include "extensions/browser/extension_function.h"
 #include "extensions/common/api/system_network.h"
 #include "net/base/network_interfaces.h"
 
 namespace extensions {
 namespace api {
 
 class SystemNetworkGetNetworkInterfacesFunction
     : public UIThreadExtensionFunction {
  public:
   DECLARE_EXTENSION_FUNCTION("system.network.getNetworkInterfaces",
                              SYSTEM_NETWORK_GETNETWORKINTERFACES)
 
   SystemNetworkGetNetworkInterfacesFunction();
 
  protected:
   ~SystemNetworkGetNetworkInterfacesFunction() override;
 
   // ExtensionFunction:
   ResponseAction Run() override;
 
  private:
-  void GetListOnFileThread();
-  void HandleGetListError();
-  void SendResponseOnUIThread(const net::NetworkInterfaceList& interface_list);
+  void SendResponseOnUIThread(
+      std::unique_ptr<net::NetworkInterfaceList> interface_list);
 };
 
 }  // namespace api
 }  // namespace extensions
 
 #endif  // EXTENSIONS_BROWSER_API_SYSTEM_NETWORK_SYSTEM_NETWORK_API_H_