If Math.random is called when creating the snapshot, we need seeds to
work with. Those seeds are going to be overwritten after deserializing
from the snapshot.

NOTRY=true
NOTREECHECKS=true
TBR=bmeurer@chromium.org

Review URL: https://codereview.chromium.org/1458003005

Cr-Commit-Position: refs/heads/master@{#32134}