Mojo C++ bindings: support disconnect with a reason.

mojo/public/cpp/bindings/lib/control_message_handler.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 MOJO_PUBLIC_CPP_BINDINGS_LIB_CONTROL_MESSAGE_HANDLER_H_
 #define MOJO_PUBLIC_CPP_BINDINGS_LIB_CONTROL_MESSAGE_HANDLER_H_
 
 #include <stdint.h>
 
+#include <string>
+
 #include "base/macros.h"
 #include "mojo/public/cpp/bindings/lib/serialization_context.h"
 #include "mojo/public/cpp/bindings/message.h"
 
 namespace mojo {
 namespace internal {
 
 // Handlers for request messages defined in interface_control_messages.mojom.
 class ControlMessageHandler : public MessageReceiverWithResponderStatus {
  public:
   static bool IsControlMessage(const Message* message);
 
   explicit ControlMessageHandler(uint32_t interface_version);
   ~ControlMessageHandler() override;
 
   // Call the following methods only if IsControlMessage() returned true.
   bool Accept(Message* message) override;
   // Takes ownership of |responder|.
   bool AcceptWithResponder(Message* message,
                            MessageReceiverWithStatus* responder) override;
 
+  uint32_t disconnect_custom_reason() const {
+    return disconnect_custom_reason_;
+  }
+
+  const std::string& disconnect_description() const {
+    return disconnect_description_;
+  }
+
  private:
   bool Run(Message* message, MessageReceiverWithStatus* responder);
   bool RunOrClosePipe(Message* message);
 
   uint32_t interface_version_;
   SerializationContext context_;
 
+  uint32_t disconnect_custom_reason_ = 0;
+  std::string disconnect_description_;
+
   DISALLOW_COPY_AND_ASSIGN(ControlMessageHandler);
 };
 
 }  // namespace internal
 }  // namespace mojo
 
 #endif  // MOJO_PUBLIC_CPP_BINDINGS_LIB_CONTROL_MESSAGE_HANDLER_H_