The cookieEnabled attribute must
return true if the user agent attempts to handle cookies according to the cookie specification,
and false if it ignores cookie change requests. [COOKIES]
The yieldForStorageUpdates() method,
when invoked, must, if the storage mutex is owned by the event loop of
the task that resulted in the method being called, release the
storage mutex so that it is once again free. Otherwise, it must do nothing.