Keep track of when a socket has been destroyed

runtime/bin/eventhandler.h

 // 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.
 
 #ifndef BIN_EVENTHANDLER_H_
 #define BIN_EVENTHANDLER_H_
 
 #include "bin/builtin.h"
 #include "bin/isolate_data.h"
 
 namespace dart {
 namespace bin {
 
 // Flags used to provide information and actions to the eventhandler
 // when sending a message about a file descriptor. These flags should
 // be kept in sync with the constants in socket_impl.dart. For more
 // information see the comments in socket_impl.dart
 enum MessageFlags {
   kInEvent = 0,
   kOutEvent = 1,
   kErrorEvent = 2,
   kCloseEvent = 3,
+  kDestroyedEvent = 4,
   kCloseCommand = 8,
   kShutdownReadCommand = 9,
   kShutdownWriteCommand = 10,
   kListeningSocket = 16,
   kPipe = 17,
 };
 
 }  // namespace bin
 }  // namespace dart
 
@@ skipping 34 matching lines @@
 
  private:
   friend class EventHandlerImplementation;
   EventHandlerImplementation delegate_;
 };
 
 }  // namespace bin
 }  // namespace dart
 
 #endif  // BIN_EVENTHANDLER_H_