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Before starting ARC container or VM try to load a snapshot if available.
ARC data snapshots are loaded only for MGS. If there is no snapshot or
the process fails, start ARC session as usual.

BUG=b:161221001
TEST=components_unittests
TEST=unit_tests

Change-Id: I7e222f9abd11b0471a40a475c73931886582bf55
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2498488
Auto-Submit: Polina Bondarenko <pbond@chromium.org>
Commit-Queue: Polina Bondarenko <pbond@chromium.org>
Reviewed-by: Oleksandr Peletskyi <peletskyi@chromium.org>
Reviewed-by: Yusuke Sato <yusukes@chromium.org>
Cr-Commit-Position: refs/heads/master@{#829117}