Revert of Remove IPC::BrokerableAttachment.

ipc/ipc_mojo_handle_attachment.cc

 // Copyright (c) 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/ipc_mojo_handle_attachment.h"
 
 #include <utility>
 
 #include "build/build_config.h"
 
 namespace IPC {
 namespace internal {
 
 MojoHandleAttachment::MojoHandleAttachment(mojo::ScopedHandle handle)
     : handle_(std::move(handle)) {}
 
 MojoHandleAttachment::~MojoHandleAttachment() {
 }
 
 MessageAttachment::Type MojoHandleAttachment::GetType() const {
-  return Type::MOJO_HANDLE;
+  return TYPE_MOJO_HANDLE;
 }
 
+#if defined(OS_POSIX)
+base::PlatformFile MojoHandleAttachment::TakePlatformFile() {
+  NOTREACHED();
+  return base::kInvalidPlatformFile;
+}
+#endif  // OS_POSIX
+
 mojo::ScopedHandle MojoHandleAttachment::TakeHandle() {
   return std::move(handle_);
 }
 
 }  // namespace internal
 }  // namespace IPC