After further review, this is not an init param at all.  It's just something that you maybe have to use when configuring a servlet from XML?

Here's the place where I found it:

http://java.dzone.com/articles/http-and-https-proxies-jetty

In the section called "Updates to web.xml".  From his description, it sounds like it would just break without it if we got it wrong.  I don't know how that maps to our world since we're not configuring via XML.

I tried deleting this from my code and everything seems to work just fine, so I'm just going to leave it out for now.