It's currently unused, but when I tried to use it to check some behavior, this brokenness has confused me a lot. Now that I understand what's going on, I already have a test and a fix.
Created attachment 59050 [details] proposed fix
Committed <http://trac.webkit.org/changeset/61415>.
http://trac.webkit.org/changeset/61415 might have broken Qt Linux Release minimal The following changes are on the blame list: http://trac.webkit.org/changeset/61416 http://trac.webkit.org/changeset/61414 http://trac.webkit.org/changeset/61415