We should make an automatic roller that runs third_party/closure_compiler/roll_closure_compiler (or accomplishes the same goal) and commits the result if all is well.

third_party/closure_compiler/roll_closure_compiler currently:
- pulls down the source from closure's github
- builds stuff (using ant)
- spits out a sample commit message

The only thing it probably needs to do more than this is:
- run some tests
- try to compile the code that previously compiled cleanly (in theory)
- be able to run headlessly/automatedly

So it's possible to re-use the script or maybe rewrite in Python.