Update status file.

tests/lib/lib.status

Index: tests/lib/lib.status
diff --git a/tests/lib/lib.status b/tests/lib/lib.status
index ec3f2b9350f6ae6354e2692c65ad53ab9d298c5a..cb0632a7b91b34ff50de835292a59b013064b255 100644
--- a/tests/lib/lib.status
+++ b/tests/lib/lib.status
@@ -130,6 +130,9 @@ async/catch_errors8_test: Fail # Timer interface not supported: dartbug.com/7728
 async/run_zoned8_test: Fail # Timer interface not supported: dartbug.com/7728.
 
 
+[ $compiler == dart2js && $checked ]
+convert/utf85_test: Pass, Slow # Issue 12029.
+
 [ $compiler == dart2js && $browser ]
 async/timer_not_available_test: Fail, OK # only meant to test when there is no way to
                                          # implement timer (currently only in d8)