The following revision refers to this bug:
  https://chromium.googlesource.com/chromiumos/platform/imageloader/+/65ec9883a1615af935f79056b290b226047d51eb

commit 65ec9883a1615af935f79056b290b226047d51eb
Author: Xiaochu Liu <xiaochu@chromium.org>
Date: Thu Aug 17 23:30:27 2017

Reland "Mount ext4 components."

This is a patch to read the fs-type from the manifest and pass it
over to the helper process that does the mounting.

BUG= chromium:752990 
TEST=autotest platform_ImageLoaderServer & unittest & mount escpr
component in production.

Change-Id: Ifaed4640dcf4b82e1ce08b4516c199f5ba61ed1b
Reviewed-on: https://chromium-review.googlesource.com/614779
Commit-Ready: Xiaochu Liu <xiaochu@chromium.org>
Tested-by: Xiaochu Liu <xiaochu@chromium.org>
Reviewed-by: Eric Caruso <ejcaruso@chromium.org>
Reviewed-by: Xiaochu Liu <xiaochu@chromium.org>

[modify] https://crrev.com/65ec9883a1615af935f79056b290b226047d51eb/component.h
[add] https://crrev.com/65ec9883a1615af935f79056b290b226047d51eb/testdata/ext4_component/imageloader.json
[modify] https://crrev.com/65ec9883a1615af935f79056b290b226047d51eb/.presubmitignore
[add] https://crrev.com/65ec9883a1615af935f79056b290b226047d51eb/testdata/ext4_component/manifest.json
[modify] https://crrev.com/65ec9883a1615af935f79056b290b226047d51eb/verity_mounter.h
[modify] https://crrev.com/65ec9883a1615af935f79056b290b226047d51eb/verity_mounter.cc
[modify] https://crrev.com/65ec9883a1615af935f79056b290b226047d51eb/component_unittest.cc
[modify] https://crrev.com/65ec9883a1615af935f79056b290b226047d51eb/helper_process.h
[add] https://crrev.com/65ec9883a1615af935f79056b290b226047d51eb/testdata/ext4_component/image.ext4
[modify] https://crrev.com/65ec9883a1615af935f79056b290b226047d51eb/test_utilities.cc
[modify] https://crrev.com/65ec9883a1615af935f79056b290b226047d51eb/component.cc
[modify] https://crrev.com/65ec9883a1615af935f79056b290b226047d51eb/ipc.proto
[add] https://crrev.com/65ec9883a1615af935f79056b290b226047d51eb/testdata/ext4_component/imageloader.sig.1
[modify] https://crrev.com/65ec9883a1615af935f79056b290b226047d51eb/helper_process.cc
[modify] https://crrev.com/65ec9883a1615af935f79056b290b226047d51eb/mount_helper.cc
[modify] https://crrev.com/65ec9883a1615af935f79056b290b226047d51eb/imageloader_unittest.cc
[modify] https://crrev.com/65ec9883a1615af935f79056b290b226047d51eb/test_utilities.h
[modify] https://crrev.com/65ec9883a1615af935f79056b290b226047d51eb/mock_helper_process.h
[add] https://crrev.com/65ec9883a1615af935f79056b290b226047d51eb/testdata/ext4_component/table