This method exists as a hook for subclasses that may have custom
threading needs within their EventTableModels. By default, this method
will wrap the given
source in a SwingThreadProxyList if it
is not already a SwingThreadProxyList. Subclasses may replace this logic
and return either a custom ThreadProxyEventList of their choosing, or
null or the
source unchanged in order
to indicate that NO ThreadProxyEventList is desired.
In these cases it is expected that some external mechanism will ensure
that threading is handled correctly.