Revert of 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