trousers: copy memory in secure way (part 1)

BUG=chromium:1020667
TEST=Build ok.
TEST=CQ
TEST=manually enroll and login on chell

Change-Id: I17f389f3abfa15b4007fe1ed0be2e238454da06f
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/third_party/trousers/+/2407932
Reviewed-by: Andrey Pronin <apronin@chromium.org>
Reviewed-by: Leo Lai <cylai@google.com>
Tested-by: joe Chou <yich@google.com>
Commit-Queue: joe Chou <yich@google.com>
5 files changed