It seems ReadWriteLock is not used and it is only implemented for some environments so it requires some #if maintenance. Perhaps we should remove it (or find some use for it).
A related discussion from 3 years ago suggests the possibility of removing this class as well - https://bugs.webkit.org/show_bug.cgi?id=30713#c4
Created attachment 173111 [details] 1st try
Comment on attachment 173111 [details] 1st try Should be fine.
Comment on attachment 173111 [details] 1st try Clearing flags on attachment: 173111 Committed r135206: <http://trac.webkit.org/changeset/135206>
All reviewed patches have been landed. Closing bug.