Revert "Add lock to a file handle 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 215 matching lines @@
 }
 
 
 static void ReadFileThread(uword args) {
   Handle* handle = reinterpret_cast<Handle*>(args);
   handle->ReadSyncCompleteAsync();
 }
 
 
 void Handle::ReadSyncCompleteAsync() {
-  ScopedLock lock(this);
   ASSERT(pending_read_ != NULL);
   ASSERT(pending_read_->GetBufferSize() >= kStdOverlappedBufferSize);
 
   DWORD buffer_size = pending_read_->GetBufferSize();
   if (GetFileType(handle_) == FILE_TYPE_CHAR) {
     buffer_size = kStdOverlappedBufferSize;
   }
   DWORD bytes_read = 0;
   BOOL ok = ReadFile(handle_,
                      pending_read_->GetBufferStart(),
@@ skipping 1053 matching lines @@
 
 
 void EventHandlerImplementation::Shutdown() {
   Notify(kShutdownId, 0, 0);
 }
 
 }  // namespace bin
 }  // namespace dart
 
 #endif  // defined(TARGET_OS_WINDOWS)