Don't issue new directory reads, if we already got unhandled data.

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 380 matching lines @@
 
 bool DirectoryWatchHandle::IsClosed() {
   return IsClosing() && pending_read_ == NULL;
 }
 
 
 bool DirectoryWatchHandle::IssueRead() {
   ScopedLock lock(this);
   // It may have been started before, as we start the directory-handler when
   // we create it.
-  if (pending_read_ != NULL) return true;
+  if (pending_read_ != NULL || data_ready_ != NULL) return true;
   OverlappedBuffer* buffer = OverlappedBuffer::AllocateReadBuffer(kBufferSize);
   ASSERT(completion_port_ != INVALID_HANDLE_VALUE);
   BOOL ok = ReadDirectoryChangesW(handle_,
                                   buffer->GetBufferStart(),
                                   buffer->GetBufferSize(),
                                   recursive_,
                                   events_,
                                   NULL,
                                   buffer->GetCleanOverlapped(),
                                   NULL);
@@ skipping 952 matching lines @@
 
 
 void EventHandlerImplementation::Shutdown() {
   SendData(kShutdownId, 0, 0);
 }
 
 }  // namespace bin
 }  // namespace dart
 
 #endif  // defined(TARGET_OS_WINDOWS)