It was enabled in the cleanup made in http://trac.webkit.org/changeset/64176 This breaks the build on MSVC 64bit.
Created attachment 66883 [details] Patch
Comment on attachment 66883 [details] Patch LGTM
Comment on attachment 66883 [details] Patch Clearing flags on attachment: 66883 Committed r66991: <http://trac.webkit.org/changeset/66991>
All reviewed patches have been landed. Closing bug.