"fix" standalone/io/sleep_test.dart on Windows

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.
 
 # WARNING:
 # Tests using the multitest feature where failure is expected should *also* be
 # listed in tests/lib/analyzer/analyze_tests.status without the "standalone"
 # prefix.
 
 package/invalid_uri_test: Fail, OK # CompileTimeErrors intentionally
@@ skipping 199 matching lines @@
 package/scenarios/invalid/non_existent_packages_file_test: Crash, OK # Analyzer exits on invalid package config
 package/scenarios/invalid/invalid_utf8_test: Crash, OK # Analyzer exits on invalid package config
 package/scenarios/invalid/invalid_package_name_test: Crash, OK # Analyzer exits on invalid package config
 package/scenarios/invalid/same_package_twice_test: Crash, OK # Analyzer exits on invalid package config
 
 [ $system == windows ]
 io/skipping_dart2js_compilations_test: Fail # Issue 19551.
 verbose_gc_to_bmu_test: Skip
 io/platform_resolved_executable_test/06: RuntimeError  # Issue 23641
 io/process_sync_test: Pass, Timeout  # Issue 24596
+io/sleep_test: Pass, Fail # Issue 25757
 
 [ $arch != ia32 && $arch != x64 && $arch != simarm && $arch != simarmv5te && $mode == debug ]
 verified_mem_test: Skip  # Not yet implemented.
 
 [ ($runtime == vm || $runtime == dart_precompiled) && $mode == debug && $builder_tag == asan ]
 full_coverage_test: Skip  # Timeout.
 io/file_lock_test: Skip  # Timeout.
 io/test_runner_test: Skip  # Timeout.
 io/http_client_stays_alive_test: Skip  # Timeout.
 
@@ skipping 65 matching lines @@
 
 # Overriding these flags are not supported in product mode.
 [ $mode == product ]
 no_profiler_test: SkipByDesign
 no_support_coverage_test: SkipByDesign
 no_support_debugger_test: SkipByDesign
 no_support_disassembler_test: SkipByDesign
 no_support_il_printer_test: SkipByDesign
 no_support_service_test: SkipByDesign
 no_support_timeline_test: SkipByDesign