Defaults VERSION to the current checkout revision
Defaults VERSION to the current checkout revision

It's easy to work with than specifying monotonically increasing version numbers.

Review: https://codereview.appspot.com/6851135/

nicko96/Chrome-Infra,nicko96/Chrome-Infra,nicko96/Chrome-Infra,nicko96/Chrome-Infra,nicko96/Chrome-Infra