http://dev.w3.org/html5/spec/Overview.html#storage-mutex describes the required behavior. After we leave JavaScript, we must be sure the storage mutex has been released. At the end of evaluate(), if localStorage has been instantiated, tell it to release any locks that may be applicable.
Created attachment 38698 [details] Patch v1
Committed r47846: <http://trac.webkit.org/changeset/47846>