Make SharedMemoryHandle a class on windows.

ipc/handle_win.h

 // Copyright 2015 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 IPC_HANDLE_WIN_H_
 #define IPC_HANDLE_WIN_H_
 
 #include <windows.h>
 
 #include "ipc/ipc_export.h"
@@ skipping 10 matching lines @@
     // A placeholder value to be used by the receiving IPC channel, since the
     // permissions information is only used by the broker process.
     INVALID,
     // The new HANDLE will have the same permissions as the old HANDLE.
     DUPLICATE,
     // The new HANDLE will have file read and write permissions.
     FILE_READ_WRITE,
     MAX_PERMISSIONS = FILE_READ_WRITE
   };
 
+  HandleWin();
   HandleWin(const HANDLE& handle, Permissions permissions);
 
   HANDLE get_handle() const { return handle_; }
   void set_handle(HANDLE handle) { handle_ = handle; }
   Permissions get_permissions() const { return permissions_; }
 
  private:
   HANDLE handle_;
   Permissions permissions_;
 };
 
 template <>
 struct IPC_EXPORT ParamTraits<HandleWin> {
   typedef HandleWin param_type;
   static void Write(Message* m, const param_type& p);
   static bool Read(const Message* m, base::PickleIterator* iter, param_type* p);
   static void Log(const param_type& p, std::string* l);
 };
 
 }  // namespace IPC
 
 #endif  // IPC_HANDLE_WIN_H_