Explicitly handle listen sockets and connection sockets differently in Linux and Mac OS eventhandler

runtime/bin/eventhandler.h

 // Copyright (c) 2011, 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"
 
 // The event handler delegation class is OS specific.
 #if defined(TARGET_OS_LINUX)
 #include "bin/eventhandler_linux.h"
 #elif defined(TARGET_OS_MACOS)
 #include "bin/eventhandler_macos.h"
 #elif defined(TARGET_OS_WINDOWS)
 #include "bin/eventhandler_win.h"
 #else
 #error Unknown target os.
 #endif
 
-/*
- * Keep these constant in sync with the dart poll event identifiers.
- */
-enum Message {
+// 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,
-  kErrorEvent,
-  kCloseEvent,
-  kCloseCommand,
+  kOutEvent = 1,
+  kErrorEvent = 2,
+  kCloseEvent = 3,
+  kCloseCommand = 8,
+  kListeningSocket = 16,
 };
 
 
 class EventHandler {
  public:
   void SendData(intptr_t id, Dart_Port dart_port, intptr_t data) {
     delegate_.SendData(id, dart_port, data);
   }
 
   static EventHandler* StartEventHandler() {
     EventHandler* handler = new EventHandler();
     handler->delegate_.StartEventHandler();
     return handler;
   }
 
  private:
   EventHandlerImplementation delegate_;
 };
 
 
 #endif  // BIN_EVENTHANDLER_H_