Fold //ipc/mojo into //ipc.

ipc/mojo/ipc_mojo_message_helper.h

-// 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.
-
-#ifndef IPC_MOJO_IPC_MOJO_MESSAGE_HELPER_H_
-#define IPC_MOJO_IPC_MOJO_MESSAGE_HELPER_H_
-
-#include "ipc/ipc_export.h"
-#include "ipc/ipc_message.h"
-#include "mojo/public/cpp/system/message_pipe.h"
-
-namespace IPC {
-
-// Reads and writes |mojo::MessagePipe| from/to |Message|.
-class IPC_MOJO_EXPORT MojoMessageHelper {
- public:
-  static bool WriteMessagePipeTo(base::Pickle* message,
-                                 mojo::ScopedMessagePipeHandle handle);
-  static bool ReadMessagePipeFrom(const base::Pickle* message,
-                                  base::PickleIterator* iter,
-                                  mojo::ScopedMessagePipeHandle* handle);
-
- private:
-  MojoMessageHelper();
-};
-
-}  // namespace IPC
-
-#endif  // IPC_MOJO_IPC_MOJO_MESSAGE_HELPER_H_