Skip mirrors_reader_test on mobile safari.

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.
 
 [ $checked && $compiler != dartanalyzer && $compiler != dart2analyzer && $runtime != dartium ]
 mirrors/regress_16321_test/01: CompileTimeError # Issue 16351
 
 [ $checked && $compiler == none && ($runtime == dartium || $runtime == drt) ]
 mirrors/regress_16321_test/01: RunTimeError # Issue 16351
 
@@ skipping 262 matching lines @@
 async/schedule_microtask5_test: Pass, Timeout # Issue 13719: Please triage this failure.
 async/timer_cancel2_test: Pass, Timeout # Issue 13719: Please triage this failure.
 
 [$compiler == none && $runtime == ContentShellOnAndroid ]
 async/stream_timeout_test: RuntimeError, Pass # Issue 19127
 convert/streamed_conversion_utf8_encode_test: Skip # Times out or passes. Issue 19127
 convert/streamed_conversion_utf8_decode_test: Skip # Times out or passes. Issue 19127
 mirrors/lazy_static_test: Skip # Times out. Issue 19127
 mirrors/mirrors_reader_test: Skip # Times out. Issue 19127
 
+[ $compiler == dart2js && $runtime == safarimobilesim ]
+mirrors/mirrors_reader_test: Skip # Times out. Issue 20806.
+
 [ $compiler == dart2dart ]
 # Deferred loading is not supported by dart2dart.
 async/deferred/deferred_in_isolate_test: Skip # Issue 17523
 
 [ $compiler == none && ($runtime == drt || $runtime == dartium || $runtime == ContentShellOnAndroid) ]
 # Dart vm does not support spawn from a dom-enabled isolate.
 async/deferred/deferred_in_isolate_test: RuntimeError # Issue 16209
 
 [ $compiler == dart2js && ($runtime == ie9 || $runtime == ie10 || $runtime == jsshell) ]
 async/schedule_microtask_test: Fail # Issue 9002
@@ skipping 29 matching lines @@
 
 [ $arch == simarm ]
 convert/chunked_conversion_utf88_test: Skip  # Pass, Slow Issue 12644.
 convert/utf85_test: Skip  # Pass, Slow Issue 12644.
 
 [ $compiler == dart2js ]
 profiler/metrics_num_test: Skip # Because of a int / double type test.
 
 [ $arch == simarm64 ]
 convert/utf85_test: Skip # Pass, Slow Issue 20111.