The following revision refers to this bug:
  https://chromium.googlesource.com/chromiumos/platform2/+/85272ef7b3d6cf261826ed0ab8c7163cb8e49d5e

commit 85272ef7b3d6cf261826ed0ab8c7163cb8e49d5e
Author: Ben Chan <benchan@chromium.org>
Date: Mon Nov 20 20:21:15 2017

cros-disks: sandbox mkfs.vfat process

FormatManager launches an external mkfs.vfat process to format a drive
into a FAT filesystem. This CL changes FormatManager to sandbox the
mkfs.vfat process via minijail.

BUG= chromium:786656 
TEST=Run unit tests.
TEST=Run platform_CrosDisksFormat test.
TEST=Manually test formatting a USB drive from Files.app.

Change-Id: Ia7901c454d36802876ff77d8b986dc72e59de4c9
Reviewed-on: https://chromium-review.googlesource.com/778119
Commit-Ready: Ben Chan <benchan@chromium.org>
Tested-by: Ben Chan <benchan@chromium.org>
Reviewed-by: Mike Frysinger <vapier@chromium.org>

[modify] https://crrev.com/85272ef7b3d6cf261826ed0ab8c7163cb8e49d5e/cros-disks/format_manager.cc
[modify] https://crrev.com/85272ef7b3d6cf261826ed0ab8c7163cb8e49d5e/cros-disks/format_manager.h

The following revision refers to this bug:
  https://chromium.googlesource.com/chromiumos/platform2/+/651ac63c53648c176d83ab37f5c4ff8215601d8f

commit 651ac63c53648c176d83ab37f5c4ff8215601d8f
Author: Ben Chan <benchan@chromium.org>
Date: Tue Nov 21 21:34:37 2017

cros-disks: mark existing mounts as private when sandboxing mkfs.vfat

CL:786656 updated FormatManager to launch an external mkfs.vfat process
in a new mount namespace, but unnecessarily carried the "skip remarking
mounts as private" workaround from FuseMounter.

BUG= chromium:786656 
TEST=Run unit tests.
TEST=Run platform_CrosDisksFormat test.
TEST=Manually test formatting a USB drive via Files.app.

Change-Id: Id3a621e7120e7aef815ee9d7c7dc5f8d18acb7ef
Reviewed-on: https://chromium-review.googlesource.com/781099
Commit-Ready: Ben Chan <benchan@chromium.org>
Tested-by: Ben Chan <benchan@chromium.org>
Reviewed-by: Mike Frysinger <vapier@chromium.org>

[modify] https://crrev.com/651ac63c53648c176d83ab37f5c4ff8215601d8f/cros-disks/format_manager.cc