Mark mirror_printer_test as slow.

Review URL: https://codereview.chromium.org/2126643002 .
diff --git a/tests/compiler/dart2js_extra/dart2js_extra.status b/tests/compiler/dart2js_extra/dart2js_extra.status
index df4de07..6fa9843 100644
--- a/tests/compiler/dart2js_extra/dart2js_extra.status
+++ b/tests/compiler/dart2js_extra/dart2js_extra.status
@@ -10,9 +10,6 @@
 constant_javascript_semantics4_test: Fail, OK
 mirrors_used_closure_test: Fail # Issue 17939
 
-[ $compiler == dart2js && $runtime == jsshell ]
-mirror_printer_test: Pass, Slow # Issue 16473
-
 [ $compiler == dart2js && $checked ]
 variable_type_test/03: Fail, OK
 variable_type_test/01: Fail, OK
@@ -85,5 +82,5 @@
 [ $compiler == dart2js && $runtime == ff && $system == windows ]
 consistent_index_error_string_test: Pass, Slow # Issue 25940
 
-[ $compiler == dart2js && $runtime == ff && $system == linux ]
-mirror_printer_test: Pass, Slow # Issue 25940
+[ $compiler == dart2js ]
+mirror_printer_test: Pass, Slow # Issue 25940, 16473