Reviewed by Adam Barth.

        Another pass at releasing the storage mutex.
        https://bugs.webkit.org/show_bug.cgi?id=28904

        Another pass at releasing the storage mutex (when applicable) when we finish
        executing JavaScript.  http://dev.w3.org/html5/spec/Overview.html#storage-mutex
        describes the required behavior.

        As it turns out, https://bugs.webkit.org/show_bug.cgi?id=28789 didn't solve
        the problem correctly.  First of all, I missed that events and timeouts go
        through a different call path.  Second of all, I didn't consider recursion
        correctly.  Third of all, my check to see if LocalStorage is alive actually
        instantiates it if it isn't yet.  Fourth, I forgot DOM_STORAGE guards around
        it.  So I'm reverting that change completely and doing it more cleanly.
        Unfortunately, the solution isn't as portable (and thus I've left out the JSC
        implementation for now).

        NOTE: This change now tracks recursion on function callbacks in V8.  I ran this
        by Mads Ager and Mike Belshe and they seemed to think adding the checks were
        fine.  Most callbacks are asynchronous and thus wouldn't be nested.  The few
        scenareos where you can have nested callbacks probably should have always been
        protected by a recursion guard.

        Unfortunately, this can't be tested without a hook added to the layout test
        controllers since the lock is (by design) not supposed to be observable by
        JavaScript.  https://bugs.webkit.org/show_bug.cgi?id=28906

        * bindings/js/ScriptController.cpp:
        (WebCore::ScriptController::evaluate): revert
        * bindings/v8/ScriptController.cpp:
        (WebCore::ScriptController::evaluate): revert
        * bindings/v8/V8Proxy.cpp:
        (WebCore::V8Proxy::runScript):
            Add releaseStorageMutex call.  A small amount of clean up.
        (WebCore::V8Proxy::callFunction):
            Add releaseStorageMutex call.  A small amount of clean up.
        (WebCore::V8Proxy::releaseStorageMutex):
            Check to see if localStorage has been instantiated.  If so, tell it to
            unlock all storage areas.
        * bindings/v8/V8Proxy.h:
        * page/PageGroup.h:
        (WebCore::PageGroup::hasLocalStorage):  Make hasLocalStorage public.

git-svn-id: http://svn.webkit.org/repository/webkit/trunk@47973 268f45cc-cd09-0410-ab3c-d52691b4dbfc