- Add a minimal implementation of Capability.

runtime/bin/io_service.cc

 // Copyright (c) 2013, 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 "bin/dartutils.h"
 #include "bin/directory.h"
 #include "bin/file.h"
 #include "bin/io_buffer.h"
 #include "bin/io_service.h"
 #include "bin/secure_socket.h"
@@ skipping 35 matching lines @@
     switch (request_id.Value()) {
   IO_SERVICE_REQUEST_LIST(CASE_REQUEST);
       default:
         UNREACHABLE();
     }
   }
 
   CObjectArray result(CObject::NewArray(2));
   result.SetAt(0, request[0]);
   result.SetAt(1, response);
+  ASSERT(reply_port_id != ILLEGAL_PORT);
   Dart_PostCObject(reply_port_id, result.AsApiCObject());
 }
 
 
 Dart_Port IOService::GetServicePort() {
   Dart_Port result = Dart_NewNativePort("IOService",
                                         IOServiceCallback,
                                         true);
   return result;
 }
 
 
 void FUNCTION_NAME(IOService_NewServicePort)(Dart_NativeArguments args) {
   Dart_SetReturnValue(args, Dart_Null());
   Dart_Port service_port = IOService::GetServicePort();
   if (service_port != ILLEGAL_PORT) {
     // Return a send port for the service port.
     Dart_Handle send_port = Dart_NewSendPort(service_port);
     Dart_SetReturnValue(args, send_port);
   }
 }
 
 
 }  // namespace bin
 }  // namespace dart