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

mojo/public/cpp/bindings/lib/interface_endpoint_client.cc

 // 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.
 
 #include "mojo/public/cpp/bindings/interface_endpoint_client.h"
 
 #include <stdint.h>
 
 #include <utility>
 
@@ skipping 263 matching lines @@
   if (encountered_error_)
     return;
   encountered_error_ = true;
 
   // The callbacks may hold on to resources. There is no need to keep them any
   // longer.
   async_responders_.clear();
 
   control_message_proxy_.OnConnectionError();
 
-  if (!error_handler_.is_null())
+  if (!error_handler_.is_null()) {
     error_handler_.Run();
+  } else if (!error_with_reason_handler_.is_null()) {
+    // Make a copy on the stack. If we directly pass a reference to a member of
+    // |control_message_handler_|, that reference will be invalidated as soon as
+    // the user destroys the interface endpoint.
+    std::string description = control_message_handler_.disconnect_description();
+    error_with_reason_handler_.Run(
+        control_message_handler_.disconnect_custom_reason(), description);
+  }
 }
 
 bool InterfaceEndpointClient::HandleValidatedMessage(Message* message) {
   DCHECK_EQ(handle_.id(), message->interface_id());
   DCHECK(!encountered_error_);
 
   if (message->has_flag(Message::kFlagExpectsResponse)) {
     MessageReceiverWithStatus* responder =
         new ResponderThunk(weak_ptr_factory_.GetWeakPtr(), task_runner_);
     bool ok = false;
@@ skipping 25 matching lines @@
     return responder->Accept(message);
   } else {
     if (mojo::internal::ControlMessageHandler::IsControlMessage(message))
       return control_message_handler_.Accept(message);
 
     return incoming_receiver_->Accept(message);
   }
 }
 
 }  // namespace mojo