Fix csslib test failures on IE10.

pkg/pkg.status

Index: pkg/pkg.status
diff --git a/pkg/pkg.status b/pkg/pkg.status
index 55fffe912e5c145074ae46bbc00307b26ff4866d..e75c7f9f5b5e3e000289a3f887c8e63aad7ce852 100644
--- a/pkg/pkg.status
+++ b/pkg/pkg.status
@@ -205,10 +205,6 @@ source_maps/test/vlq_test: RuntimeError # A VLQ test checks for large numbers th
 intl/test/find_default_locale_browser_test: Fail
 intl/test/date_time_format_http_request_test: Skip # Timeout.
 
-[ $runtime == ie9 || $runtime == ie10 ]
-csslib/test/declaration_test: RuntimeError # Issue 20274
-csslib/test/mixin_test: RuntimeError # Issue 20274
-
 [ $runtime == ie9 ]
 mime/test/mime_multipart_transformer_test: Skip # No typed_data on IE9.
 typed_data/test/typed_buffers_test: Fail, Crash # No typed_data on IE9.