The fast/forms/input-auto-fill-button.html layout test is failing on GTK since it was added on r181408 (http://trac.webkit.org/changeset/181408). https://build.webkit.org/results/GTK%20Linux%2064-bit%20Release%20%28Tests%29/r181476%20%286927%29/fast/forms/input-auto-fill-button-pretty-diff.html
This test has been removed.