http://trac.webkit.org/changeset/136323 introduced testrunner.closeIdleLocalStorageDatabases() but WebKitTestRunner does not implement it yet.
This causes the following test to fail for all WK2 ports:
The tests which rely off of this functionality are remnants of QT support. See https://bugs.webkit.org/show_bug.cgi?id=160529.
Disregard previous comment, this bug remains valid and to be implemented in WK2 ports.