Sources are here https://android.googlesource.com/platform/system/core in libsync directory.

Chromium has a copy of libsync:

https://chromium.googlesource.com/chromium/src/+/master/third_party/libsync

AFAICT it's not being used by any component inside Chrome. We probably want to remove it to avoid someone using the deprecated API.

This is used for testing purposes by my experimental patches that add explicit sync support to chrome. I think we want to keep this testing purposes, just like we have a copy of libdrm, minigbm, etc. in third_party for testing purposes.

However, we should make this an external repo dependency instead of a copy of the files.

When building for a real ChromeOS device we'd use the system version of libsync just like we do with libdrm and minigbm.

The following revision refers to this bug:
  https://chrome-internal.googlesource.com/chromeos/manifest-internal/+/2f7484aa21cd253d781d97ccb4be47a39ca60d47

commit 2f7484aa21cd253d781d97ccb4be47a39ca60d47
Author: Dominik Behr <dbehr@google.com>
Date: Tue Jun 06 01:34:00 2017

The following revision refers to this bug:
  https://chromium.googlesource.com/chromiumos/manifest/+/34bf37975758ea446430286c6b314278a6d3a3d9

commit 34bf37975758ea446430286c6b314278a6d3a3d9
Author: Dominik Behr <dbehr@chromium.org>
Date: Tue Jun 06 01:33:57 2017

add libsync to manifest

BUG= chromium:715846 
TEST=none

Change-Id: If06b3117c4f9c8bed29d72a645a24500fa265265
Signed-off-by: Dominik Behr <dbehr@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/523811
Reviewed-by: Mike Frysinger <vapier@chromium.org>

[modify] https://crrev.com/34bf37975758ea446430286c6b314278a6d3a3d9/full.xml

The following revision refers to this bug:
  https://chrome-internal.googlesource.com/chromeos/manifest-internal/+/2f7484aa21cd253d781d97ccb4be47a39ca60d47

commit 2f7484aa21cd253d781d97ccb4be47a39ca60d47
Author: Dominik Behr <dbehr@google.com>
Date: Tue Jun 06 01:34:00 2017

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/1b5feabc7f79238b5a95ab429a5aae55d603100e

commit 1b5feabc7f79238b5a95ab429a5aae55d603100e
Author: Ricky Liang <jcliang@chromium.org>
Date: Tue Jun 13 03:12:00 2017

third_party: allow building with system libsync

Add a GN variable to control whether to build Chrome with the system or
the bundled libsync.

BUG=b:32690003,  chromium:715846 
TEST=Build Chrome for Chrome OS with use_system_libsync=true with
     simplechrome

Change-Id: I2dd942fbbf4e67d44b0b220062b5a1e42c9f5261
Reviewed-on: https://chromium-review.googlesource.com/530210
Commit-Queue: Ricky Liang <jcliang@chromium.org>
Reviewed-by: David Reveman <reveman@chromium.org>
Cr-Commit-Position: refs/heads/master@{#478879}
[modify] https://crrev.com/1b5feabc7f79238b5a95ab429a5aae55d603100e/third_party/libsync/BUILD.gn

The following revision refers to this bug:
  https://chromium.googlesource.com/chromiumos/overlays/board-overlays/+/1933b5a0bd44702baffbb6598d2e5b933fc77e13

commit 1933b5a0bd44702baffbb6598d2e5b933fc77e13
Author: Dominik Behr <dbehr@chromium.org>
Date: Sat Aug 05 01:08:14 2017

arc-camera3-hal-intel-ipu3: switch from arc-camera3-libsync to libsync

There is now an shared library libsync ebuild to be used on Chrome OS,
switch arc-camera3 to use it.

BUG= chromium:715846 
TEST=emerge arc-camera3 and verify with objdump it links with libsync.so
CQ-DEPEND=Ic88a5521b5ba7bf603094f3698e32a926712ddea,I353badaac935499fcf7df7e9b1e022b3e7ac341b,Ib094a0517b701a7903d65f0615352e0343f23dd3

Change-Id: If6339fe30261c28456753759983886c10f27513c
Signed-off-by: Dominik Behr <dbehr@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/598492

[modify] https://crrev.com/1933b5a0bd44702baffbb6598d2e5b933fc77e13/baseboard-poppy/media-libs/arc-camera3-hal-intel-ipu3/arc-camera3-hal-intel-ipu3-9999.ebuild

The following revision refers to this bug:
  https://chromium.googlesource.com/chromiumos/overlays/chromiumos-overlay/+/1f9fbc2051f881f30a132a78c40eacaac8db582b

commit 1f9fbc2051f881f30a132a78c40eacaac8db582b
Author: Dominik Behr <dbehr@chromium.org>
Date: Sat Aug 05 01:08:14 2017

media-libs/libsync: add new ebuild

Add ebuild for shared libsync.so library for Chrome and other programs to
use.

BUG= chromium:715846 
TEST=emerge-kevin libsync
CQ-DEPEND=Ic88a5521b5ba7bf603094f3698e32a926712ddea

Change-Id: I353badaac935499fcf7df7e9b1e022b3e7ac341b
Signed-off-by: Dominik Behr <dbehr@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/571305
Reviewed-by: Mike Frysinger <vapier@chromium.org>

[add] https://crrev.com/1f9fbc2051f881f30a132a78c40eacaac8db582b/media-libs/libsync/files/strlcpy.c
[add] https://crrev.com/1f9fbc2051f881f30a132a78c40eacaac8db582b/media-libs/libsync/libsync-0.0.1-r1.ebuild
[add] https://crrev.com/1f9fbc2051f881f30a132a78c40eacaac8db582b/media-libs/libsync/files/libsync.pc.template
[add] https://crrev.com/1f9fbc2051f881f30a132a78c40eacaac8db582b/media-libs/libsync/files/0001-libsync-add-prototype-for-strlcpy.patch
[add] https://crrev.com/1f9fbc2051f881f30a132a78c40eacaac8db582b/media-libs/libsync/files/Makefile
[add] https://crrev.com/1f9fbc2051f881f30a132a78c40eacaac8db582b/media-libs/libsync/libsync-9999.ebuild

The following revision refers to this bug:
  https://chromium.googlesource.com/chromiumos/overlays/chromiumos-overlay/+/70bf1f16753cade012ade9577c1fe55b615ff10f

commit 70bf1f16753cade012ade9577c1fe55b615ff10f
Author: Dominik Behr <dbehr@chromium.org>
Date: Sat Aug 05 01:08:15 2017

arc-camera3: switch from arc-camera3-libsync to libsync

There is now an shared library libsync ebuild to be used on Chrome OS,
switch arc-camera3 to use it.

BUG= chromium:715846 
TEST=emerge arc-camera3 and verify with objdump it links with libsync.so
CQ-DEPEND=I353badaac935499fcf7df7e9b1e022b3e7ac341b,If6339fe30261c28456753759983886c10f27513c

Change-Id: Ic88a5521b5ba7bf603094f3698e32a926712ddea
Signed-off-by: Dominik Behr <dbehr@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/572337

[delete] https://crrev.com/1f9fbc2051f881f30a132a78c40eacaac8db582b/media-libs/arc-camera3-libsync/arc-camera3-libsync-9999.ebuild
[delete] https://crrev.com/1f9fbc2051f881f30a132a78c40eacaac8db582b/media-libs/arc-camera3-libsync/arc-camera3-libsync-0.0.1-r77.ebuild
[modify] https://crrev.com/70bf1f16753cade012ade9577c1fe55b615ff10f/media-libs/arc-camera3-test/arc-camera3-test-9999.ebuild
[modify] https://crrev.com/70bf1f16753cade012ade9577c1fe55b615ff10f/media-libs/arc-camera3/arc-camera3-9999.ebuild

The following revision refers to this bug:
  https://chromium.googlesource.com/chromiumos/platform/arc-camera/+/51eeb268d269af0914582a1df73998a317e1136a

commit 51eeb268d269af0914582a1df73998a317e1136a
Author: Dominik Behr <dbehr@chromium.org>
Date: Sat Aug 05 01:08:15 2017

arc-camera3-hal-intel-ipu3: drop "android" from sync.h include

BUG= chromium:715846 
TEST=TEST=emerge arc-camera3-hal-intel-ipu3
CQ-DEPEND=Ic88a5521b5ba7bf603094f3698e32a926712ddea

Change-Id: Ib094a0517b701a7903d65f0615352e0343f23dd3
Signed-off-by: Dominik Behr <dbehr@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/602580

[modify] https://crrev.com/51eeb268d269af0914582a1df73998a317e1136a/hal/intel/psl/ipu3/CameraBuffer.cpp

The following revision refers to this bug:
  https://chromium.googlesource.com/chromiumos/overlays/chromiumos-overlay/+/476f9e956c871bbb3b75091653602899cbdcfcdd

commit 476f9e956c871bbb3b75091653602899cbdcfcdd
Author: Mike Frysinger <vapier@chromium.org>
Date: Thu Oct 05 01:47:11 2017

libsync: block arc-camera3-libsync

This package installs the same files as the old package.

BUG= chromium:715846 
TEST=precq passes

Change-Id: I26ce5da236c993a65daa349fc6c0a73718ec1218
Reviewed-on: https://chromium-review.googlesource.com/700014
Commit-Ready: Mike Frysinger <vapier@chromium.org>
Tested-by: Dominik Behr <dbehr@chromium.org>
Tested-by: Mike Frysinger <vapier@chromium.org>
Reviewed-by: Dominik Behr <dbehr@chromium.org>

[modify] https://crrev.com/476f9e956c871bbb3b75091653602899cbdcfcdd/media-libs/libsync/libsync-9999.ebuild
[rename] https://crrev.com/476f9e956c871bbb3b75091653602899cbdcfcdd/media-libs/libsync/libsync-0.0.1-r2.ebuild