Update co19 status on firefox and chrome.

tests/lib/lib.status

Index: tests/lib/lib.status
diff --git a/tests/lib/lib.status b/tests/lib/lib.status
index 54fef3d81b3363e36122cbc7e4e98443b0f7c05f..9a2068fa037777064cd620f8efa82167f9e27783 100644
--- a/tests/lib/lib.status
+++ b/tests/lib/lib.status
@@ -206,9 +206,12 @@ mirrors/mirrors_used_get_name2_test: RuntimeError
 [ $runtime == ff ]
 # FF setTimeout can fire early: https://bugzilla.mozilla.org/show_bug.cgi?id=291386
 convert/streamed_conversion_utf8_decode_test: Pass, Slow  # Issue 12029
-convert/streamed_conversion_utf8_encode_test: Pass, Slow # Issue 12029
 mirrors/mirrors_reader_test: Timeout, Slow, RuntimeError # Issue 16589
 
+[ $runtime == chrome || $runtime == ff]
+convert/streamed_conversion_utf8_encode_test: Pass, Slow, Timeout # Issue 12029
+async/slow_consumer2_test: Pass, Timeout # Please triage this issue.
+
 [ $compiler == dart2js ]
 typed_data/typed_data_hierarchy_int64_test: RuntimeError # Issue 10275
 typed_data/int32x4_bigint_test: RuntimeError # Issue 1533