Fix compilation warnings in Windows event handler

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 692 matching lines @@
 
   write_thread_exists_ = false;
   write_monitor_->Notify();
   write_monitor_->Exit();
 }
 
 
 void StdHandle::WriteSyncCompleteAsync() {
   ASSERT(pending_write_ != NULL);
 
   DWORD bytes_written = -1;

[Ivan Posva, 2015/01/06 23:27:45]

Interestingly this was not being warned about before. If anything this should be
a zero.

   BOOL ok = WriteFile(handle_,
                       pending_write_->GetBufferStart(),
                       pending_write_->GetBufferSize(),
                       &bytes_written,
                       NULL);
   if (!ok) {
     bytes_written = 0;
   }
   thread_wrote_ += bytes_written;
   OVERLAPPED* overlapped = pending_write_->GetCleanOverlapped();
@@ skipping 233 matching lines @@
 
 bool DatagramSocket::IssueRecvFrom() {
   ScopedLock lock(this);
   ASSERT(completion_port_ != INVALID_HANDLE_VALUE);
   ASSERT(pending_read_ == NULL);
 
   OverlappedBuffer* buffer = OverlappedBuffer::AllocateRecvFromBuffer(1024);
 
   DWORD flags;
   flags = 0;
-  int len;
   int rc = WSARecvFrom(socket(),
                        buffer->GetWASBUF(),
                        1,
                        NULL,
                        &flags,
                        buffer->from(),
                        buffer->from_len_addr(),
                        buffer->GetCleanOverlapped(),
                        NULL);
   if (rc == NO_ERROR || WSAGetLastError() == WSA_IO_PENDING) {
@@ skipping 268 matching lines @@
       HandleConnect(client_socket, bytes, buffer);
       break;
     }
     default:
       UNREACHABLE();
   }
 }
 
 
 EventHandlerImplementation::EventHandlerImplementation() {
-  intptr_t result;
   completion_port_ =
       CreateIoCompletionPort(INVALID_HANDLE_VALUE, NULL, NULL, 1);
   if (completion_port_ == NULL) {
     FATAL("Completion port creation failed");
   }
   shutdown_ = false;
 }
 
 
 EventHandlerImplementation::~EventHandlerImplementation() {
@@ skipping 98 matching lines @@
 
 
 void EventHandlerImplementation::Shutdown() {
   SendData(kShutdownId, 0, 0);
 }
 
 }  // namespace bin
 }  // namespace dart
 
 #endif  // defined(TARGET_OS_WINDOWS)