Which Javascript minifier (cruncher) does the same things that the one Google uses for its JS APIs?

Question

I am a Google Maps API (javascript) developer. I have noticed that Google uses a Javascript minifier that has the following features:

1. Shortens variables, prope

Answer 1

Here are the minifiers I know of: Dean Edwards' packer; YUI Compressor; JSMIN; and Dojo compressor

In addition to these, the GWT compiler does quite a bit to make efficient JavaScript files out of Java files. It wouldn't surprise me if that is what they use.