Provide mechanism to close immediately to Dart bindings

sky/engine/bindings/mojo_natives.cc

 // Copyright 2014 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 "sky/engine/config.h"
 #include "sky/engine/bindings/mojo_natives.h"
 
 #include <stdio.h>
 #include <string.h>
 #include <vector>
@@ skipping 698 matching lines @@
   int64_t data;
 };
 
 void MojoHandleWatcher_SendControlData(Dart_NativeArguments arguments) {
   int64_t control_handle = 0;
   int64_t client_handle = 0;
   CHECK_INTEGER_ARGUMENT(arguments, 0, &control_handle, InvalidArgument);
   CHECK_INTEGER_ARGUMENT(arguments, 1, &client_handle, InvalidArgument);
 
   Dart_Handle send_port_handle = Dart_GetNativeArgument(arguments, 2);
-  Dart_Port send_port_id = 0;
+  Dart_Port send_port_id = ILLEGAL_PORT;
   if (!Dart_IsNull(send_port_handle)) {
     Dart_Handle result = Dart_SendPortGetId(send_port_handle, &send_port_id);
     if (Dart_IsError(result)) {
       SetInvalidArgumentReturn(arguments);
       return;
     }
   }
 
   int64_t data = 0;
   CHECK_INTEGER_ARGUMENT(arguments, 3, &data, InvalidArgument);
@@ skipping 18 matching lines @@
   uint32_t num_handles = 0;
   MojoResult res = MojoReadMessage(
       control_handle, bytes, &num_bytes, nullptr, &num_handles, 0);
   if (res != MOJO_RESULT_OK) {
     SetNullReturn(arguments);
     return;
   }
 
   Dart_Handle list = Dart_NewList(3);
   Dart_ListSetAt(list, 0, Dart_NewInteger(cd.handle));
-  Dart_ListSetAt(list, 1, Dart_NewSendPort(cd.port));
+  if (cd.port != ILLEGAL_PORT) {
+    Dart_ListSetAt(list, 1, Dart_NewSendPort(cd.port));
+  }
   Dart_ListSetAt(list, 2, Dart_NewInteger(cd.data));
   Dart_SetReturnValue(arguments, list);
 }
 
 static int64_t mojo_control_handle = MOJO_HANDLE_INVALID;
 void MojoHandleWatcher_SetControlHandle(Dart_NativeArguments arguments) {
   int64_t control_handle;
   CHECK_INTEGER_ARGUMENT(arguments, 0, &control_handle, InvalidArgument);
   mojo_control_handle = control_handle;
   Dart_SetIntegerReturnValue(arguments, static_cast<int64_t>(MOJO_RESULT_OK));
 }
 
 void MojoHandleWatcher_GetControlHandle(Dart_NativeArguments arguments) {
   Dart_SetIntegerReturnValue(arguments, mojo_control_handle);
 }
 
 }  // namespace blink