http/tests/w3c/html/semantics/forms/textfieldselection/selection.html frequently fails, especially on debug builds:

https://webkit-test-results.webkit.org/dashboards/flakiness_dashboard.html#showAllRuns=true&tests=http%2Ftests%2Fw3c%2Fhtml%2Fsemantics%2Fforms%2Ftextfieldselection%2Fselection.html

@@ -1,13 +1,3 @@
 
 
-PASS test if selection text is correct for input 
-PASS test if selection text is correct for textarea 
-PASS test if non-ascii selection text is correct for input 
-PASS test if non-ascii selection text is correct for textarea 
-PASS test SelectionStart offset for input 
-FAIL test SelectionStart offset for textarea assert_equals: SelectionStart offset without selection expected 10 but got 0
-PASS test SelectionEnd offset for input 
-FAIL test SelectionEnd offset for textarea assert_equals: SelectionEnd offset without selection expected 10 but got 0
-PASS test SelectionDirection for input 
-PASS test SelectionDirection for textarea 
-
+Harness Error. harness_status.status = 2 , harness_status.message = null