This is sibling to Bug 1440421. As part of a general effort to bring Node into the Firefox build system, and to support GitHub-using teams more generally, I'd like to make more uniform the on-disk layout of Git/Node projects in mozilla-central. For debugger.html, that looks like checking in a cloned version (minus .git!) of the upstream repository with each landing into mozilla-central, and adjusting relevant build scripts to update the checked in clone. This is not urgent -- it just makes testing and experimentation easier. In a Vidyo call with jlast, he suggested that this should happen _after_ the old debugger is removed, so I've marked this as depending on Bug 1314057.