Make Completers asynchronous.

tests/standalone/standalone.status

 # 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.
 
 package/invalid_uri_test: Fail, OK # Fails intentionally
 
 [ $runtime == vm ]
 # Fails because checked-in dart executable is not up to date.
 io/test_runner_test: Fail
 # Fails because checked-in dart executable is not up to date.
 # Skip this because it is leaving temp directories behind when it fails.
 io/skipping_dart2js_compilations_test: Skip
 
 [ $runtime == vm && ( $system == windows ) ]
 io/raw_socket_test: Pass, Fail # Issue 8901
 
 [ $runtime == vm ]
 package/package_isolate_test: Fail # http://dartbug.com/7520.
 io/raw_server_socket_cancel_test: Pass, Fail, Timeout # Issue 8675
+io/http_server_early_client_close2_test: Fail # http://dartbug.com/10408
 
 [ $runtime == vm && $checked ]
 # These tests have type errors on purpose.
 io/process_invalid_arguments_test: Fail, OK
 io/directory_invalid_arguments_test: Fail, OK
 io/file_invalid_arguments_test: Fail, OK
 io/socket_invalid_arguments_test: Fail, OK
 io/stdout_bad_argument_test: Fail, OK
 # These test have type errors on purpose and take very long to run in
 # checked mode with no benefit. Skip.
@@ skipping 88 matching lines @@
 *: Skip
 
 [ $arch == simarm ]
 *: Skip
 
 [ $arch == mips ]
 *: Skip
 
 [ $arch == simmips ]
 *: Skip