Mark convert/streamed_conversion_json_utf8_decode_test as slow

tests/lib/lib.status

 # 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.
 
 [ $unchecked ]
 mirrors/redirecting_factory_different_type_test: SkipByDesign # Tests type checks.
 
 [ $compiler == dart2js ]
 async/schedule_microtask6_test: RuntimeError # global error handling is not supported. Issue 5958
 
@@ skipping 211 matching lines @@
 typed_data/int32x4_bigint_test: RuntimeError # Issue 1533
 typed_data/int64_list_load_store_test: RuntimeError # Issue 10275
 
 [ $runtime == opera ]
 async/multiple_timer_test: Pass, Fail # Probably issue 14734
 
 [ $runtime == opera && $system == windows]
 # TODO(efortuna): Investigate.
 async/timer_test: Fail, Pass
 
+[ $runtime == vm ]
+convert/streamed_conversion_json_utf8_decode_test: Pass, Slow # Infrequent timeouts.
+
 [ ($runtime == vm || $runtime == dart_precompiled || $runtime == dart_app) ]
 async/timer_not_available_test: Fail, OK
 mirrors/native_class_test: Fail, OK # This test is meant to run in a browser.
 mirrors/deferred_type_test: CompileTimeError, OK # Don't have a multitest marker for dynamic compile time errors.
 
 [ $compiler == none || $compiler == precompiler || $compiler == dart2app || $compiler == dart2appjit ]
 async/timer_not_available_test: SkipByDesign # only meant to test when there is no way to implement timer (currently only in d8)
 
 mirrors/symbol_validation_test: RuntimeError # Issue 13596
 
@@ skipping 121 matching lines @@
 mirrors/*: SkipByDesign
 
 [ $noopt || $compiler == precompiler ]
 convert/chunked_conversion_utf88_test: Pass, Timeout
 convert/utf85_test: Pass, Timeout
 
 [ $arch == simdbc || $arch == simdbc64 ]
 # TODO(vegorov) LoadField bytecode supports only up to 256 fields. Need a long
 # version.
 mirrors/accessor_cache_overflow_test: Skip