Fix race condition between signal handler and main thread.

runtime/bin/file_impl.dart

 // Copyright (c) 2012, 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.
 
 class _FileInputStream extends _BaseDataInputStream implements InputStream {
   _FileInputStream(File file) {
     _file = file.openSync();
     _length = _file.lengthSync();
     _streamMarkedClosed = true;
     _checkScheduleCallbacks();
@@ skipping 672 matching lines @@
 
 
 class _RandomAccessFile implements RandomAccessFile {
   _RandomAccessFile(int this._id, String this._name)
     : _scheduler = new _FileOperationScheduler(),
       _asyncUsed = false;
 
   void close() {
     _asyncUsed = true;
     var handler = (_closeHandler != null) ? _closeHandler : () => null;
-    var handleOpenResult = (result, ignored) {
+    var handleCloseResult = (result, ignored) {
       if (result != -1) {
         _id = result;
         handler();
       } else if (_errorHandler != null) {
         _errorHandler("Cannot close file: $_name");
       }
     };
     var operation = new _CloseOperation(_id);
-    _scheduler.enqueue(operation, handleOpenResult);
+    _scheduler.enqueue(operation, handleCloseResult);
   }
 
   void closeSync() {
     if (_asyncUsed) {
       throw new FileIOException(
           "Mixed use of synchronous and asynchronous API");
     }
     var id = _FileUtils.close(_id);
     if (id == -1) {
       throw new FileIOException("Cannot close file: $_name");
@@ skipping 369 matching lines @@
   var _readByteHandler;
   var _readListHandler;
   var _noPendingWriteHandler;
   var _positionHandler;
   var _setPositionHandler;
   var _truncateHandler;
   var _lengthHandler;
   var _flushHandler;
   var _errorHandler;
 }