Fix Windows event-handler, where write can 'complete' with 0 bytes written.

runtime/bin/eventhandler_win.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 "platform/globals.h"
 #if defined(TARGET_OS_WINDOWS)
 
 #include "bin/eventhandler.h"
 
 #include <winsock2.h>  // NOLINT
@@ skipping 1103 matching lines @@
 
   DeleteIfClosed(handle);
 }
 
 
 void EventHandlerImplementation::HandleWrite(Handle* handle,
                                              int bytes,
                                              OverlappedBuffer* buffer) {
   handle->WriteComplete(buffer);
 
-  if (bytes > 0) {
+  if (bytes >= 0) {
     if (!handle->IsError() && !handle->IsClosing()) {
       int event_mask = 1 << kOutEvent;
       if ((handle->mask() & event_mask) != 0) {
         DartUtils::PostInt32(handle->port(), event_mask);
       }
     }
-  } else if (bytes == 0) {
-    HandleClosed(handle);
   } else {
     HandleError(handle);
   }
 
   DeleteIfClosed(handle);
 }
 
 
 void EventHandlerImplementation::HandleDisconnect(
     ClientSocket* client_socket,
@@ skipping 158 matching lines @@
 
 
 void EventHandlerImplementation::Shutdown() {
   SendData(kShutdownId, 0, 0);
 }
 
 }  // namespace bin
 }  // namespace dart
 
 #endif  // defined(TARGET_OS_WINDOWS)