Make FileInputStream and FileOutputStream actually asynchronous.

tests/standalone/src/StreamPipeTest.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.
 //
 // VMOptions=
 // VMOptions=--short_socket_read
 // VMOptions=--short_socket_write
 // VMOptions=--short_socket_read --short_socket_write
 
 #library("StreamPipeTest");
@@ skipping 180 matching lines @@
   var tempDir = new Directory('');
   tempDir.createTempSync();
   var dstFileName = tempDir.path + "/readline_test1.dat";
   var dstFile = new File(dstFileName);
   dstFile.createSync();
   var dstStream = dstFile.openOutputStreamSync();
 
   srcStream.closeHandler = () {
     dstStream.write([32]);
     dstStream.close();
-    var src = srcFile.openSync();
-    var dst = dstFile.openSync();
-    var srcLength = src.lengthSync();
-    var dstLength = dst.lengthSync();
-    Expect.equals(srcLength + 1, dstLength);
-    Expect.isTrue(compareFileContent(srcFileName,
-                                     dstFileName,
-                                     count: srcLength));
-    dst.setPositionSync(srcLength);
-    var data = new List<int>(1);
-    var read2 = dst.readListSync(data, 0, 1);
-    Expect.equals(32, data[0]);
-    src.closeSync();
-    dst.closeSync();
-    dstFile.deleteSync();
-    tempDir.deleteSync();
+    dstStream.closeHandler = () {
+      var src = srcFile.openSync();
+      var dst = dstFile.openSync();
+      var srcLength = src.lengthSync();
+      var dstLength = dst.lengthSync();
+      Expect.equals(srcLength + 1, dstLength);
+      Expect.isTrue(compareFileContent(srcFileName,
+                                       dstFileName,
+                                       count: srcLength));
+      dst.setPositionSync(srcLength);
+      var data = new List<int>(1);
+      var read2 = dst.readListSync(data, 0, 1);
+      Expect.equals(32, data[0]);
+      src.closeSync();
+      dst.closeSync();
+      dstFile.deleteSync();
+      tempDir.deleteSync();
+    };
   };
 
   srcStream.pipe(dstStream, close: false);
 }
 
 
 // Test piping two copies of one file to another.
 testFileToFilePipe3() {
   String srcFileName =
       getDataFilename("tests/standalone/src/readline_test1.dat");
@@ skipping 36 matching lines @@
   srcStream.pipe(dstStream, close: false);
 }
 
 
 main() {
   testFileToFilePipe1();
   testFileToFilePipe2();
   testFileToFilePipe3();
   PipeServerGame echoServerGame = new PipeServerGame.start();
 }