Use OnceCallback for Mojo binding connection error handlers.

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>
-
 #include "base/bind.h"
 #include "base/location.h"
 #include "base/logging.h"
 #include "base/macros.h"
 #include "base/memory/ptr_util.h"
 #include "base/single_thread_task_runner.h"
 #include "base/stl_util.h"
 #include "mojo/public/cpp/bindings/associated_group.h"
 #include "mojo/public/cpp/bindings/associated_group_controller.h"
 #include "mojo/public/cpp/bindings/interface_endpoint_controller.h"
@@ skipping 281 matching lines @@
   encountered_error_ = true;
 
   // Response callbacks may hold on to resource, and there's no need to keep
   // them alive any longer. Note that it's allowed that a pending response
   // callback may own this endpoint, so we simply move the responders onto the
   // stack here and let them be destroyed when the stack unwinds.
   AsyncResponderMap responders = std::move(async_responders_);
 
   control_message_proxy_.OnConnectionError();
 
-  if (!error_handler_.is_null()) {
-    base::Closure error_handler = std::move(error_handler_);
-    error_handler.Run();
-  } else if (!error_with_reason_handler_.is_null()) {
-    ConnectionErrorWithReasonCallback error_with_reason_handler =
-        std::move(error_with_reason_handler_);
+  if (error_handler_) {
+    std::move(error_handler_).Run();
+  } else if (error_with_reason_handler_) {
     if (reason) {
-      error_with_reason_handler.Run(reason->custom_reason, reason->description);
+      std::move(error_with_reason_handler_)
+          .Run(reason->custom_reason, reason->description);
     } else {
-      error_with_reason_handler.Run(0, std::string());
+      std::move(error_with_reason_handler_).Run(0, std::string());
     }
   }
 }
 
 void InterfaceEndpointClient::QueryVersion(
     const base::Callback<void(uint32_t)>& callback) {
   control_message_proxy_.QueryVersion(callback);
 }
 
 void InterfaceEndpointClient::RequireVersion(uint32_t version) {
@@ skipping 71 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