The Tor Browser / file revision

 Bugs to fix:

 - make content-length generation not rely on .available() returning the entire

   size of the body stream's contents -- some sort of wrapper (but how does that

   work for the unscriptable method WriteSegments, which is good to support from

   a performance standpoint?)

 Ideas for future improvements:

 - add API to disable response buffering which, when called, causes errors when

   you try to do anything other than write to the body stream (i.e., modify

   headers or status line) once you've written anything to it -- useful when

   storing the entire response in memory is unfeasible (e.g., you're testing

   >4GB download characteristics)

 - add an API which performs asynchronous response processing (instead of

   nsIHttpRequestHandler.handle, which must construct the response before control

   returns; |void asyncHandle(request, response)|) -- useful, and can it be done

   in JS?

 - other awesomeness?