Mark corelib/regexp/pcre_test as slow on dart2js

tests/corelib/corelib.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.
 
 [ $compiler == dart2dart]
 bool_from_environment2_test: Skip
 bool_from_environment_default_value_test: Skip
 bool_from_environment_test: Skip
 from_environment_const_type_test: Skip
 from_environment_const_type_undefined_test: Skip
@@ skipping 103 matching lines @@
 hash_set_test/01: RuntimeError # Issue 11551
 integer_to_string_test/01: RuntimeError # Issue 1533
 iterable_return_type_test/01: RuntimeError # Issue 20085
 iterable_return_type_test/02: RuntimeError # Dart2js does not support Uint64*.
 
 big_integer_*: Skip # VM specific test.
 bit_twiddling_bigint_test: RuntimeError # Requires bigint support.
 compare_to2_test: RuntimeError, OK    # Requires bigint support.
 string_base_vm_test: RuntimeError, OK # VM specific test.
 nan_infinity_test/01: Fail # Issue 11551
+regexp/pcre_test: Pass, Slow # Issue 21593
+
 
 [ $compiler == dart2js && $runtime == none ]
 *: Fail, Pass # TODO(ahe): Triage these tests.
 
 [ $compiler == dart2js && $runtime == chromeOnAndroid ]
 list_as_map_test: Pass, Slow # TODO(kasperl): Please triage.
 
 [ $compiler == dart2js && ($runtime == firefox || $runtime == safari || $runtime == chrome || $runtime == drt) ]
 
 [ $compiler == dart2js && ($runtime == safari || $runtime == safarimobilesim) ]
@@ skipping 90 matching lines @@
 num_parse_test: RuntimeError  # Issue 15316
 num_parse_test/01: RuntimeError  # Issue 15316
 
 [ $system == windows && $arch == x64 ]
 stopwatch_test: Skip  # Flaky test due to expected performance behaviour.
 
 [ $runtime != d8 ]
 # JSCRE does not pass all of the tests ported for irregexp.
 # Ignore all of the tests until irregexp is fully ported.
 regexp/*: Skip