platform/mac/fast/forms/input-list-button-size.html is failing on all of the Mac bots. The bot history seemed to point to http://trac.webkit.org/changeset/113137 , so I built WebKit r113136 and then r113137, and indeed the test passed with r113136 and failed with r113137.
I looks like this test just needs to be added to the Skipped list since the Datalist feature was disabled.
Added the test to the Skipped list: http://trac.webkit.org/changeset/113239
Oh, I'm sorry for this.
list-button is a part of ENABLE_DATALIST, so this is an expected failure.
Also, we're going to remove the list-button in Bug 83117.