Use the return value of vm native methods to set the return value,

lib/mirrors.cc

 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #include "vm/bootstrap_natives.h"
 
 #include "platform/json.h"
 #include "include/dart_api.h"
 #include "include/dart_debugger_api.h"
 #include "vm/dart_entry.h"
@@ skipping 10 matching lines @@
   // Get the port id from the SendPort instance.
   const Object& id_obj = Object::Handle(DartLibraryCalls::PortGetId(port));
   if (id_obj.IsError()) {
     Exceptions::PropagateError(Error::Cast(id_obj));
     UNREACHABLE();
   }
   ASSERT(id_obj.IsSmi() || id_obj.IsMint());
   Integer& id = Integer::Handle();
   id ^= id_obj.raw();
   Dart_Port port_id = static_cast<Dart_Port>(id.AsInt64Value());
-  const Bool& is_local = Bool::Handle(Bool::Get(PortMap::IsLocalPort(port_id)));
-  arguments->SetReturn(is_local);
+  return Bool::Get(PortMap::IsLocalPort(port_id));
 }
 
 
 // TODO(turnidge): Add Map support to the dart embedding api instead
 // of implementing it here.
 static Dart_Handle CoreLib() {
   Dart_Handle core_lib_name = Dart_NewString("dart:core");
   return Dart_LookupLibrary(core_lib_name);
 }
 
@@ skipping 882 matching lines @@
 }
 
 
 void HandleMirrorsMessage(Isolate* isolate,
                           Dart_Port reply_port,
                           const Instance& message) {
   UNIMPLEMENTED();
 }
 
 }  // namespace dart