Mark process_stdin_transform_unsubscribe_test as Pass, Timeout

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.
 
 io/raw_socket_test: Pass, RuntimeError # Issue 28288
@@ 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 ]
 verbose_gc_to_bmu_test: Skip
 io/process_sync_test: Pass, Timeout # Issue 24596
 io/sleep_test: Pass, Fail # Issue 25757
 io/http_server_early_client_close2_test: Pass, Crash  # Issue 28197
+io/process_stdin_transform_unsubscribe_test: Pass, Timeout # Issue #28558
 
 [ $system == windows && $compiler != dart2analyzer ]
 io/platform_resolved_executable_test/06: RuntimeError  # Issue 23641
 io/skipping_dart2js_compilations_test: Fail # Issue 19551.
 io/socket_info_ipv6_test: RuntimeError # Issue 27876
 
 [ $system == windows && $compiler == dart2analyzer ]
 package/package_isolate_test: Crash # Issue 28645
 package/scenarios/empty_packages_file/empty_packages_file_noimports_test: Crash # Issue 28645
 package/scenarios/empty_packages_file/empty_packages_file_option_test: Crash, Pass # Issue 28645
@@ skipping 178 matching lines @@
 io/socket_source_address_test: SkipByDesign
 io/socket_bind_test: SkipByDesign
 io/http_proxy_advanced_test: SkipByDesign
 io/http_ipv6_test: SkipByDesign
 io/socket_ipv6_test: SkipByDesign
 io/socket_info_ipv6_test: SkipByDesign
 
 [ $builder_tag == asan && $arch == x64 ]
 io/process_detached_test: Pass, Slow
 io/named_pipe_script_test: RuntimeError