Fix async test that uses temp directories.

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 742 matching lines @@
     } catch (Exception ex) {
       wrongExceptionCaught = true;
     }
     Expect.equals(true, exceptionCaught);
     Expect.equals(true, !wrongExceptionCaught);
     input.deleteSync();
   }
 
   // Tests stream exception handling after file was closed.
   static void testCloseExceptionStream() {
+    asyncTestStarted();
     List<int> buffer = new List<int>(42);
     File file = new File(tempDirectory.path + "/out_close_exception_stream");
     file.createSync();
     InputStream input = file.openInputStreamSync();
     input.closeHandler = () {
       Expect.isTrue(input.closed);
       Expect.isNull(input.readInto(buffer, 0, 12));
       OutputStream output = file.openOutputStreamSync();
       output.close();
       Expect.throws(() => output.writeFrom(buffer, 0, 12));
       file.deleteSync();
+      asyncTestDone("testCloseExceptionStream");
     };
   }
 
   // Tests buffer out of bounds exception.
   static void testBufferOutOfBoundsException() {
     bool exceptionCaught = false;
     bool wrongExceptionCaught = false;
     File file = new File(tempDirectory.path + "/out_buffer_out_of_bounds");
     RandomAccessFile openedFile = file.openSync(FileMode.WRITE);
     try {
@@ skipping 358 matching lines @@
       testWriteVariousLists();
       testDirectory();
       testDirectorySync();
     });
   }
 }
 
 main() {
   FileTest.testMain();
 }