Update FileTest.dart to aboid potential Windows failure

tests/standalone/src/FileTest.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.
 //
 // Dart test program for testing file I/O.
 
 #import("dart:io");
 #import("dart:isolate");
 
 class MyListOfOneElement implements List {
@@ skipping 111 matching lines @@
             Expect.equals(false, writeDone);
             output.noPendingWriteHandler = () {
               output.close();
 
               // Now read the contents of the file just written.
               List<int> buffer2 = new List<int>(42);
               file = new File(outFilename);
               input = file.openInputStream();
               input.dataHandler = () {
                 bytesRead = input.readInto(buffer2, 0, 42);
-                Expect.isTrue(input.closed);
                 Expect.equals(42, bytesRead);
                 // Now compare the two buffers to check if they are identical.
                 for (int i = 0; i < buffer1.length; i++) {
                   Expect.equals(buffer1[i],  buffer2[i]);
                 }
-                // Delete the output file.
-                file.deleteSync();
-                Expect.isFalse(file.existsSync());
-                asyncTestDone("testReadWriteStream");
+                input.closeHandler = () {
+                  // Delete the output file.
+                  file.deleteSync();
+                  Expect.isFalse(file.existsSync());
+                  asyncTestDone("testReadWriteStream");
+                };
               };
             };
           };
         };
       };
     };
   }
 
   static void testRead() {
     // Read a file and check part of it's contents.
@@ skipping 994 matching lines @@
       testWriteVariousLists();
       testDirectory();
       testDirectorySync();
     });
   }
 }
 
 main() {
   FileTest.testMain();
 }