ipc: Create AttachmentBrokerPrivileged and AttachmentBrokerUnprivileged.

ipc/attachment_broker_unprivileged.h

+// 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.
+
+#ifndef IPC_ATTACHMENT_BROKER_UNPRIVILEGED_H_
+#define IPC_ATTACHMENT_BROKER_UNPRIVILEGED_H_
+
+#include "ipc/attachment_broker.h"
+#include "ipc/ipc_export.h"
+
+namespace IPC {
+
+class Sender;
+
+// This abstract subclass of AttachmentBroker is intended for use in
+// non-privileged processes.
+class IPC_EXPORT AttachmentBrokerUnprivileged : public IPC::AttachmentBroker {
+ public:
+  AttachmentBrokerUnprivileged();
+  ~AttachmentBrokerUnprivileged() override;
+
+  void set_sender(IPC::Sender* sender) { sender_ = sender; }
+
+ protected:
+  IPC::Sender* get_sender() { return sender_; }
+
+ private:
+  // |sender_| is used to send Messages to the privileged broker process.
+  // |sender_| must live at least as long as this instance.
+  IPC::Sender* sender_;
+  DISALLOW_COPY_AND_ASSIGN(AttachmentBrokerUnprivileged);
+};
+
+}  // namespace IPC
+
+#endif  // IPC_ATTACHMENT_BROKER_UNPRIVILEGED_H_