Comment 83 for bug 25830

Created an attachment (id=130378)
proof-of-concept. DO NOT CHECK THIS IN.

this unfortunately includes the "part 2" patch from bug 78919 as well as the
patch for bug 120045 :( sorry about that

I hope the concept is still visible, which is mainly passing an nsIDispatchable
to nsIExternalHelperAppService::DoContent. I'm not very good at coming up with
names, so said name might suck; feel free to suggest a different one.

oh, and you _do_not_ want to run a normal mozilla with this exact patch. you
will be sorry if you do. (that's because it forces all externally handled
content to display as text/plain, for testing purposes)

next step: clean this up a bit, allow this to be called from the helper app
dialog, implement ui for it