IPC: Remove unnecessary conversions of BrokerableAttachment.

ipc/attachment_broker_unprivileged_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_ATTACHMENT_BROKER_UNPRIVILEGED_WIN_H_
 #define IPC_ATTACHMENT_BROKER_UNPRIVILEGED_WIN_H_
 
 #include "ipc/attachment_broker_unprivileged.h"
 #include "ipc/handle_attachment_win.h"
 #include "ipc/ipc_export.h"
 
 namespace IPC {
 
 class BrokerableAttachment;
 
 // This class is an implementation of AttachmentBroker for the Windows platform
 // for non-privileged processes.
 class IPC_EXPORT AttachmentBrokerUnprivilegedWin
     : public IPC::AttachmentBrokerUnprivileged {
  public:
   AttachmentBrokerUnprivilegedWin();
   ~AttachmentBrokerUnprivilegedWin() override;
 
   // IPC::AttachmentBroker overrides.
-  bool SendAttachmentToProcess(BrokerableAttachment* attachment,
-                               base::ProcessId destination_process) override;
+  bool SendAttachmentToProcess(
+      const scoped_refptr<BrokerableAttachment>& attachment,
+      base::ProcessId destination_process) override;
 
   // IPC::Listener overrides.
   bool OnMessageReceived(const Message& message) override;
 
  private:
   // IPC message handlers.
   void OnWinHandleHasBeenDuplicated(
       const IPC::internal::HandleAttachmentWin::WireFormat& wire_format);
 
   DISALLOW_COPY_AND_ASSIGN(AttachmentBrokerUnprivilegedWin);
 };
 
 }  // namespace IPC
 
 #endif  // IPC_ATTACHMENT_BROKER_UNPRIVILEGED_WIN_H_