Revert "[MCR] Turn Revision into a proxy to new code."

This reverts commit 9dcc56b3c9e7a3212d0900ee23808b9402cad952.

With this patch applied, newly created revisions are sometimes not found
just after submitting an edit, until replicas have caught up.

Our best theory is that it somehow interfere with ChronologyProtector,
but we don't have a good idea how.

Also, as legoktm mentioned, the commit message is terrible and needs fixing.

Change-Id: Idf3404f3fa8f8d08a7fb2ab8268726e2c1edecfe