Make base::AutoReset moveable

This was brought up in the discussion of
https://crrev.com/c/1611240 that we should make it
moveable to avoid heap allocations when we have to
pass it around.

TBR=oshima@chromium.org
BUG=866622
TEST=base_unittests, and existing ash_unittests.

Change-Id: I7c6fb3c010c01129e6dcc8a0155bb53d35d295d4
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1613371
Reviewed-by: Ahmed Fakhry <afakhry@chromium.org>
Reviewed-by: Mitsuru Oshima <oshima@chromium.org>
Reviewed-by: kylechar <kylechar@chromium.org>
Commit-Queue: Ahmed Fakhry <afakhry@chromium.org>
Cr-Commit-Position: refs/heads/master@{#660112}
5 files changed