Convert FILE thread usage in system_network_api.cc to TaskScheduler.

extensions/browser/api/system_network/system_network_api.h

Index: extensions/browser/api/system_network/system_network_api.h
diff --git a/extensions/browser/api/system_network/system_network_api.h b/extensions/browser/api/system_network/system_network_api.h
index 38e9e6c22447185c61f921ec03f0a95f735da575..385fed466d04645c05782a86589e15748d42d49a 100644
--- a/extensions/browser/api/system_network/system_network_api.h
+++ b/extensions/browser/api/system_network/system_network_api.h
@@ -5,6 +5,8 @@
 #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"
@@ -27,9 +29,8 @@ class SystemNetworkGetNetworkInterfacesFunction
   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