Revert "validation_pool: pool.changes -> pool.candidates, pool.applied."

This reverts commit ff627b430f16161de5d62b390733984692329fe0.

BUG=chromium:557314
TEST=None

Change-Id: I057df80e2208fbce020e878d677e8b1e5f9656d0
Reviewed-on: https://chromium-review.googlesource.com/312965
Reviewed-by: Aviv Keshet <akeshet@chromium.org>
Reviewed-by: Don Garrett <dgarrett@chromium.org>
Tested-by: Simran Basi <sbasi@chromium.org>
7 files changed