IPC: Add MojoHandleAttachment

ipc/mojo/ipc_mojo_message_helper.h

Index: ipc/mojo/ipc_mojo_message_helper.h
diff --git a/ipc/mojo/ipc_mojo_message_helper.h b/ipc/mojo/ipc_mojo_message_helper.h
new file mode 100644
index 0000000000000000000000000000000000000000..efb48c33a94f61632f863c45dade97c85c9821f8
--- /dev/null
+++ b/ipc/mojo/ipc_mojo_message_helper.h
@@ -0,0 +1,29 @@
+// 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 "third_party/mojo/src/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(Message* message,
+                                 mojo::ScopedMessagePipeHandle handle);
+  static bool ReadMessagePipeFrom(const Message* message,
+                                  PickleIterator* iter,
+                                  mojo::ScopedMessagePipeHandle* handle);
+
+ private:
+  MojoMessageHelper();
+};
+
+}  // namespace IPC
+
+#endif  // IPC_MOJO_IPC_MOJO_MESSAGE_HELPER_H_