[InnocentB]

This is because Chrome has a little disassembler built into their binary-diff mechanism, so they can get really small diffs (at least on Windows; for Linux they fall back onto bsdiff).

http://dev.chromium.org/developers/design-documents/software... has some of the details. Note the ~90% reduction in size going from bsdiff to this.

I want to use this for my own stuff, because that's cool as hell, but the Courgette source has pretty major dependencies on the rest of Chromium.