Downloaded a fresh OS X DMG from ftp://ftp.mozilla.org/pub/firefox/nightly/2012-03-01-11-39-32-mozilla-central/, though I also see this in a recent build on my OS X box. Two odd items are included... FirefoxNightly.app/Contents/MacOS/jsloader/resource/ Empty directory. FirefoxNightly.app/Contents/MacOS/jssubloader/185/resource/gre/chrome/toolkit/content/global/devtools/dbg-transport.js Seems to be binary (fastload?) contents. How either of these are getting into the appdir, let alone being shipped in release builds, is rather confusing to me. Not sure if this is a bug in devtools, or a bug in the subscriptloader caching (bug 648125). Maybe both?

I'm also seeing jssubloader/185/resource/gre/chrome/toolkit/content/global/devtools/dbg-transport.js in my linux x86-64 nightly. Very strange.

I don't know if it's any help, but here are the two places where we load the debugger transport: http://mxr.mozilla.org/mozilla-central/source/toolkit/devtools/debugger/dbg-client.jsm#65 http://mxr.mozilla.org/mozilla-central/source/toolkit/devtools/debugger/server/dbg-server.jsm#76