Didn't we all assume that it disabled autosave? I observed that running http/tests/security tests changed the value of -[WebPreferences privateBrowsingEnabled] in parallel DRT processes, which is horrible, because it could then easily get picked up by -[WebView _preferencesChanged:] any time it's called for any reason.
Created attachment 221298 [details] proposed fix
Comment on attachment 221298 [details] proposed fix Clearing flags on attachment: 221298 Committed r162092: <http://trac.webkit.org/changeset/162092>
All reviewed patches have been landed. Closing bug.