validation_pool: Prep for pickling change.

Add an additional ValidationPool argument that is ignored for the sake
for an upcoming value that needs to be preserved during pickling.

BUG=chromium:549844
TEST=cbuildbot/run_tests --network

Change-Id: I0a4b1f1b96bb47f37b53ab92b7dc944fd0ac6630
Reviewed-on: https://chromium-review.googlesource.com/312116
Commit-Ready: Don Garrett <[email protected]>
Tested-by: Don Garrett <[email protected]>
Reviewed-by: David James <[email protected]>
1 file changed