Remove IPC::BrokerableAttachment.

ipc/brokerable_attachment.cc

-// 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.
-
-#include "ipc/brokerable_attachment.h"
-
-#include <stddef.h>
-
-#include "build/build_config.h"
-
-namespace IPC {
-
-// BrokerableAttachment::BrokerableAttachment ----------------------------------
-
-BrokerableAttachment::BrokerableAttachment() = default;
-
-BrokerableAttachment::~BrokerableAttachment() = default;
-
-bool BrokerableAttachment::NeedsBrokering() const {
-  return GetBrokerableType() == PLACEHOLDER;
-}
-
-BrokerableAttachment::Type BrokerableAttachment::GetType() const {
-  return TYPE_BROKERABLE_ATTACHMENT;
-}
-
-#if defined(OS_POSIX)
-base::PlatformFile BrokerableAttachment::TakePlatformFile() {
-  NOTREACHED();
-  return base::PlatformFile();
-}
-#endif  // OS_POSIX
-
-}  // namespace IPC