workaround random dart2js crash in csslib tests

pkg/pkg.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.
 
 # Don't run any test-like files that show up in packages directories. It
 # shouldn't be necessary to run "pub install" in these packages, but if you do
 # it shouldn't break the tests.
 */packages/*/*: Skip
 */*/packages/*/*: Skip
 */*/*/packages/*/*: Skip
@@ skipping 75 matching lines @@
 serialization/test/no_library_test: Fail # Issue 6490
 
 # This test cannot run under CSP because it is injecting a JavaScript polyfill
 mutation_observer: Skip
 
 [ $compiler == dart2js && $minified ]
 # The unminified unittest tests test that the real names of Dart types are
 # printed. Minified versions of these tests exist that test the behavior when
 # minified.
 unittest/test/*_unminified_test: Skip # DO NOT COPY THIS UNLESS YOU WORK ON DART2JS
+csslib: Pass, Crash # crashing randomly, see issue 12468
 
 [ $compiler == dart2js && $browser ]
 stack_trace/test/vm_test: Fail, OK # VM-specific traces
 crypto/test/sha256_test: Slow, Pass
 crypto/test/sha1_test: Slow, Pass
 csslib/test/var_test: Fail # looking for VM-specific stack traces
 
 [ $compiler == dart2js && $runtime == drt ]
 csslib/test/nested_test: Fail # crashing DRT
 third_party/html5lib/test/parser_feature_test: Fail # issue 12466
@@ skipping 87 matching lines @@
 
 # Skip tests on the VM if the package depends on dart:html
 [ $runtime == vm ]
 custom_element: Skip
 mdv: Skip
 mutation_observer: Skip
 third_party/html5lib/test/browser/browser_test: Skip
 
 [ $runtime == safari || $runtime == chrome || $runtime == ie9 || $runtime == ff || $runtime == dartium || $runtime == drt ]
 docgen/test/single_library_test: Skip # Uses dart:io