Per https://luci-milo.appspot.com/buildbot/tryserver.chromium.linux/linux_chromium_chromeos_ozone_rel_ng/284020:

There are several failures that need to be fixed before CrOS/ozone/x11 can replace CrOS/X11 for builder/development purposes.

Summary: views_aura_mus_unittests, views_mus_unittests, app_list_unittests, ash_unittests, aura_unittests, content_unittests, interactive_ui_tests, ui_chromeos_unittests, unit_tests, views_unittests, wm_unittests have failures in CrOS/ozone/x11. Perusing the builder results (https://luci-milo.appspot.com/buildbot/tryserver.chromium.linux/linux_chromium_chromeos_ozone_rel_ng/284020) suggests that a great number of these tests are related to touch event handling in Ozone/x11.

We also need to ensure the UI debugging tools for external displays (like Ctrl-Shift-D to simulate connect/disconnect) still work on Linux workstations for CrOS/ozone/x11.

AFAICT they work OK today, but there might be edge cases we need to fix.

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/ed64274506538a9770b7bf86df7eef2ecb4948b7

commit ed64274506538a9770b7bf86df7eef2ecb4948b7
Author: kylechar <kylechar@chromium.org>
Date: Mon Dec 19 21:10:33 2016

Use xvfb with Ozone CrOS.

We want to switch the majority of Ozone CrOS tests over to run with
--ozone-platform=x11. This requires that test targets with type
'windowed_test_launcher' run using xvfb.

Right now mb.py looks for the arg '--ozone-platform=x11' in the isolate
step, which requires adding a new target for each test we want to add.
Instead, just assume that if use_ozone=true and target_os="chromeos"
then we want to use xvfb.

Ozone CrOS test with type 'windowed_test_launcher' will still need to
have '--ozone-platform=x11' flag added in chromimum.chromiumos.json to
run with Ozone X11. Once most tests pass under with Ozone X11 the
default Ozone platform can be swapped to be x11 and only tests that
should run with headless will require an args entry there.

BUG= 671355 

Review-Url: https://codereview.chromium.org/2587473002
Cr-Commit-Position: refs/heads/master@{#439557}

[modify] https://crrev.com/ed64274506538a9770b7bf86df7eef2ecb4948b7/testing/buildbot/chromium.chromiumos.json
[modify] https://crrev.com/ed64274506538a9770b7bf86df7eef2ecb4948b7/testing/buildbot/gn_isolate_map.pyl
[modify] https://crrev.com/ed64274506538a9770b7bf86df7eef2ecb4948b7/tools/mb/mb.py
[modify] https://crrev.com/ed64274506538a9770b7bf86df7eef2ecb4948b7/ui/gl/BUILD.gn

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/faa7892bed1c4340b84d37abc506fbb3f17615c2

commit faa7892bed1c4340b84d37abc506fbb3f17615c2
Author: vmpstr <vmpstr@chromium.org>
Date: Wed Dec 21 02:12:21 2016

Revert of Use xvfb with Ozone CrOS. (patchset #2 id:20001 of https://codereview.chromium.org/2587473002/ )

Reason for revert:
Suspecting that this is causing intermittent bot crashes on after gl_unittests runs. See crbug.com/676128 for more details.

Original issue's description:
> Use xvfb with Ozone CrOS.
>
> We want to switch the majority of Ozone CrOS tests over to run with
> --ozone-platform=x11. This requires that test targets with type
> 'windowed_test_launcher' run using xvfb.
>
> Right now mb.py looks for the arg '--ozone-platform=x11' in the isolate
> step, which requires adding a new target for each test we want to add.
> Instead, just assume that if use_ozone=true and target_os="chromeos"
> then we want to use xvfb.
>
> Ozone CrOS test with type 'windowed_test_launcher' will still need to
> have '--ozone-platform=x11' flag added in chromimum.chromiumos.json to
> run with Ozone X11. Once most tests pass under with Ozone X11 the
> default Ozone platform can be swapped to be x11 and only tests that
> should run with headless will require an args entry there.
>
> BUG= 671355 
>
> Committed: https://crrev.com/ed64274506538a9770b7bf86df7eef2ecb4948b7
> Cr-Commit-Position: refs/heads/master@{#439557}

TBR=dpranke@chromium.org,rjkroege@chromium.org,sadrul@chromium.org,kylechar@chromium.org
# Not skipping CQ checks because original CL landed more than 1 days ago.
BUG= 671355 , 676128

Review-Url: https://codereview.chromium.org/2598483002
Cr-Commit-Position: refs/heads/master@{#439980}

[modify] https://crrev.com/faa7892bed1c4340b84d37abc506fbb3f17615c2/testing/buildbot/chromium.chromiumos.json
[modify] https://crrev.com/faa7892bed1c4340b84d37abc506fbb3f17615c2/testing/buildbot/gn_isolate_map.pyl
[modify] https://crrev.com/faa7892bed1c4340b84d37abc506fbb3f17615c2/tools/mb/mb.py
[modify] https://crrev.com/faa7892bed1c4340b84d37abc506fbb3f17615c2/ui/gl/BUILD.gn

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/39705684829e901db436c5185961acc4a37034fd

commit 39705684829e901db436c5185961acc4a37034fd
Author: kylechar <kylechar@chromium.org>
Date: Thu Jan 19 14:37:23 2017

Reland: Use xvfb with Ozone CrOS.

We want to switch the majority of Ozone CrOS tests over to run with
--ozone-platform=x11. This requires that test targets with type
'windowed_test_launcher' run using xvfb.

Right now mb.py looks for the arg '--ozone-platform=x11' in the isolate
step, which requires adding a new target for each test we want to add.
Instead, just assume that if use_ozone=true and target_os="chromeos"
then we want to use xvfb.

Ozone CrOS test with type 'windowed_test_launcher' will still need to
have '--ozone-platform=x11' flag added in chromimum.chromiumos.json to
run with Ozone X11. Once most tests pass under with Ozone X11 the
default Ozone platform can be swapped to be x11 and only tests that
should run with headless will require an args entry there.

This was originally landed in http://crrev.com/2587473002 and then
reverted. I had switched gl_unittests to type='windowed_test_launcher'.
gl_unittests for most platforms run on real hardware and this caused the
Linux GPU trybot to crash. Running gl_unittests in xvfb is required for
Ozone as there are no Ozone Chrome OS GPU trybots, so keep the extra
test target.

BUG= 671355 

Review-Url: https://codereview.chromium.org/2640133002
Cr-Commit-Position: refs/heads/master@{#444727}

[modify] https://crrev.com/39705684829e901db436c5185961acc4a37034fd/testing/buildbot/chromium.chromiumos.json
[modify] https://crrev.com/39705684829e901db436c5185961acc4a37034fd/testing/buildbot/gn_isolate_map.pyl
[modify] https://crrev.com/39705684829e901db436c5185961acc4a37034fd/tools/mb/mb.py
[modify] https://crrev.com/39705684829e901db436c5185961acc4a37034fd/ui/gl/BUILD.gn

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/6d3b7a7957c406a6dff39bc778d8ce0324a638ba

commit 6d3b7a7957c406a6dff39bc778d8ce0324a638ba
Author: kylechar <kylechar@chromium.org>
Date: Thu Mar 16 14:30:07 2017

Change default Ozone platform to Ozone X11.

When using ozone_auto_platforms=true change the default Ozone platform
to be X11 for Chrome OS and Linux Desktop. This does not change what
Ozone platforms are built. The CQ trybots already runs tests using Ozone
X11 by default, this is just to make developers are also using the same
configuration.

The Ozone platform can always be picked at runtime with
--ozone-platform=X command line flag.

BUG= 671355 

Review-Url: https://codereview.chromium.org/2730733002
Cr-Commit-Position: refs/heads/master@{#457431}

[modify] https://crrev.com/6d3b7a7957c406a6dff39bc778d8ce0324a638ba/ui/ozone/ozone.gni

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/c2087acb00eee7960339a0be34ea27d6b20e1131

commit c2087acb00eee7960339a0be34ea27d6b20e1131
Author: kylechar <kylechar@chromium.org>
Date: Tue Mar 21 18:13:59 2017

Remove mb_config Ozone platform arguments.

This added GN args is now the default, so it's not necessary.

BUG= 671355 

Review-Url: https://codereview.chromium.org/2749423004
Cr-Commit-Position: refs/heads/master@{#458475}

[modify] https://crrev.com/c2087acb00eee7960339a0be34ea27d6b20e1131/tools/mb/mb_config.pyl

+sky

The remaining issues I know of that could potentially be blocking as a follow:
1. Fixing OzonePlatform::InitializeForUI() call sites to properly specify single_process mode in tests. I fixed OzonePlatform::InitializeForGPU() call sites.
2. Run browser_tests on linux_chromium_chromeos_ozone_rel_ng, preferably with Ozone X11. This is the only test that isn't running on the Ozone CrOS trybots that runs on X11 CrOS trybots.
3. Make OSMesa output to XWindow with Ozone X11.
4. Make GLX (--use-gl=desktop) the default on Ozone X11. Right now it defaults to EGL (--use-gl=egl) because there was a crash with mus+ash and GLX.

There are bugs filed and blocking for each of those.

+oshima just FYI

A few weeks ago I ran browser_tests on Ozone headless and Ozone X11 to see what failed.

Ozone headless failures:
PPAPINaClNewlibTest.TrueTypeFont
PPAPINaClPNaClNonSfiTest.TrueTypeFont
PPAPINaClPNaClTest.TrueTypeFont

Ozone X11 failures:
BluetoothHostPairingWithInputTest.BluetoothDisableByDefault
BluetoothHostPairingNoInputTest.ForgetDevice
PPAPINaClPNaClNonSfiTest.TrueTypeFont
PPAPINaClPNaClTest.TrueTypeFont
BluetoothHostPairingNoInputTest.NoBluetoothDeviceConnected
PPAPINaClNewlibTest.TrueTypeFont
BluetoothHostPairingNoInputTest.BluetoothDeviceConnected
DesktopCaptureApiTest.ChooseDesktopMedia

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/59c10fe1fa4658261ac1ef92176e7f558a7c3687

commit 59c10fe1fa4658261ac1ef92176e7f558a7c3687
Author: kylechar <kylechar@chromium.org>
Date: Thu May 04 12:50:38 2017

Specify use_ozone=false for X11 CrOS trybots.

By default use_ozone=false if target_os="chromeos". This causes
use_11=true and the X11 Chrome OS configuration to get built. Make
trybots that have implicit GN arg use_ozone=false specify it explicitly.

This will allow the default value for use_ozone to get changed without
changing the current trybot configurations.

BUG= 671355 

Review-Url: https://codereview.chromium.org/2854923002
Cr-Commit-Position: refs/heads/master@{#469316}

[modify] https://crrev.com/59c10fe1fa4658261ac1ef92176e7f558a7c3687/tools/mb/mb_config.pyl

Would it be helpful if I asked the Chrome OS UI team to try manually adding use_ozone = true to their GN configs? Do you need more feedback from people manually using it?

(It works fine for me, of course.)

I'm working on getting browser_tests running on linux_chromium_chromeos_ozone_rel_ng and then I think we're at a state where the default could reasonably be flipped.

Having more feedback from Chrome OS UI team before that point would be great though.

i'm not sure if it's related to my use of Ozone, but I often get local test failures:
Issue 718350: HatsNotificationControllerTest unit_tests fail on my linux workstation
Issue 324217: inotify_init() failed: Too many open files

kylechar@ can you update based on which tests are still a problem?

Is this still an issue msw? I'm not seeing any failures running unit_tests with Ozone X11 or Ozone headless locally now.

I did just reopen Issue 718350 and I *think* Issue 324217 tests still flake.
Neither issue should block our X11->Ozone transition, IMO. Full steam ahead!
(it's possible those failures all occur in X11 anyway, I don't build that)

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/7385c63ec2b3606a67bb192bf96311ada07aa1c6

commit 7385c63ec2b3606a67bb192bf96311ada07aa1c6
Author: dpranke <dpranke@chromium.org>
Date: Tue Jul 11 02:15:29 2017

Remove all of the CrOS Ozone configs from MB.

Ozone is now on by default on all CrOS builds, and we don't
need to test the old x11 config any more. This CL flips
all of the CrOS builders to (implicitly) be building for Ozone,
so that we can then remove the explicit Ozone builders in a
follow-up CL.

This builder also removes the
linux_chromium_chromeos_ozone_rel_ng builder from the CQ
since would otherwise be redundant with the
linux_chromium_chromeos_rel_ng builder.

This CL also removes a couple of commented-out CQ entries for
builders that were removed as part of the work in bug 669297
(linux_chromium_chromeos_compile_dbg_ng and linux_chromium_clobber_rel_ng);
at the time I had planned to re-add them once the capacity
issues were resolved, but at this point it's unclear how
important those configs are and we may want to use the
capacity for other things, and so these comments were misleading.

R=kylechar@chromium.org, kbr@chromium.org
TBR=achuith@chromium.org, xdai@chromium.org
BUG= 671355 

Review-Url: https://codereview.chromium.org/2949093004
Cr-Commit-Position: refs/heads/master@{#485495}

[modify] https://crrev.com/7385c63ec2b3606a67bb192bf96311ada07aa1c6/chrome/browser/chromeos/login/bluetooth_host_pairing_browsertest.cc
[modify] https://crrev.com/7385c63ec2b3606a67bb192bf96311ada07aa1c6/infra/config/cq.cfg
[modify] https://crrev.com/7385c63ec2b3606a67bb192bf96311ada07aa1c6/testing/buildbot/chromium.chromiumos.json
[modify] https://crrev.com/7385c63ec2b3606a67bb192bf96311ada07aa1c6/tools/mb/mb_config.pyl

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/9dfa3c95d67ac0348f208a8cb631c606b5cfa54f

commit 9dfa3c95d67ac0348f208a8cb631c606b5cfa54f
Author: keishi <keishi@chromium.org>
Date: Tue Jul 11 10:34:20 2017

Revert of Remove all of the CrOS Ozone configs from MB. (patchset #8 id:130001 of https://codereview.chromium.org/2949093004/ )

Reason for revert:
ash_unittests are failing on ChromeOS AsanLsan bot
 crbug.com/740859 
Regression range is 485493 - 485513 so suspecting this.

Original issue's description:
> Remove all of the CrOS Ozone configs from MB.
>
> Ozone is now on by default on all CrOS builds, and we don't
> need to test the old x11 config any more. This CL flips
> all of the CrOS builders to (implicitly) be building for Ozone,
> so that we can then remove the explicit Ozone builders in a
> follow-up CL.
>
> This builder also removes the
> linux_chromium_chromeos_ozone_rel_ng builder from the CQ
> since would otherwise be redundant with the
> linux_chromium_chromeos_rel_ng builder.
>
> This CL also removes a couple of commented-out CQ entries for
> builders that were removed as part of the work in bug 669297
> (linux_chromium_chromeos_compile_dbg_ng and linux_chromium_clobber_rel_ng);
> at the time I had planned to re-add them once the capacity
> issues were resolved, but at this point it's unclear how
> important those configs are and we may want to use the
> capacity for other things, and so these comments were misleading.
>
> R=kylechar@chromium.org, kbr@chromium.org
> TBR=achuith@chromium.org, xdai@chromium.org
> BUG= 671355 
>
> Review-Url: https://codereview.chromium.org/2949093004
> Cr-Commit-Position: refs/heads/master@{#485495}
> Committed: https://chromium.googlesource.com/chromium/src/+/7385c63ec2b3606a67bb192bf96311ada07aa1c6

TBR=kylechar@chromium.org,kbr@chromium.org,fjhenigman@chromium.org,dpranke@chromium.org
# Skipping CQ checks because original CL landed less than 1 days ago.
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG= 671355 

Review-Url: https://codereview.chromium.org/2974923002
Cr-Commit-Position: refs/heads/master@{#485579}

[modify] https://crrev.com/9dfa3c95d67ac0348f208a8cb631c606b5cfa54f/chrome/browser/chromeos/login/bluetooth_host_pairing_browsertest.cc
[modify] https://crrev.com/9dfa3c95d67ac0348f208a8cb631c606b5cfa54f/infra/config/cq.cfg
[modify] https://crrev.com/9dfa3c95d67ac0348f208a8cb631c606b5cfa54f/testing/buildbot/chromium.chromiumos.json
[modify] https://crrev.com/9dfa3c95d67ac0348f208a8cb631c606b5cfa54f/tools/mb/mb_config.pyl

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/63e34448474381620aa6fce8c68b7f2c4ced7b75

commit 63e34448474381620aa6fce8c68b7f2c4ced7b75
Author: Dirk Pranke <dpranke@chromium.org>
Date: Fri Jul 14 16:27:47 2017

Re-land "Remove all of the CrOS Ozone configs from MB".

This change may affect the following builders:

  - chromium.chromiumos
    - Linux ChromiumOS Builder
    - Linux ChromiumOS Builder (dbg)
    - Linux ChromiumOS Full
  - chromium.fyi
    - Mojo ChromiumOS
  - chromium.gpu.fyi
    - Linux ChromiumOS Builder
    - Linux ChromiumOS Ozone Builder
  - chromium.memory
    - Linux Chromium OS ASan LSan Builder
    - Linux Chromium OS ASan LSan Tests (1)
    - Linux ChromiumOS MSan Builder
    - Linux ChromiumOS MSan Tests (1)
  - tryserver.chromium.linux
    - linux_chromium_chromeos_asan_rel_ng
    - linux_chromium_chromeos_compile_dbg_ng
    - linux_chromium_chromeos_compile_rel_ng
    - linux_chromium_chromeos_dbg_ng
    - linux_chromium_chromeos_msan_rel_ng
    - linux_chromium_chromeos_ozone_rel_ng
    - linux_chromium_chromeos_rel_ng

The main difference from the last attempt is that this version
removes ash_unittests, ash_content_unittests, browser_tests,
interactive_ui_tests, and unit_tests from the ASan LSan Tests config,
as they appear to be all kinds of busted.

From the original CL (crrev.com/7385c63ec2):
> Ozone is now on by default on all CrOS builds, and we don't
> need to test the old x11 config any more. This CL flips
> all of the CrOS builders to (implicitly) be building for Ozone,
> so that we can then remove the explicit Ozone builders in a
> follow-up CL.
>
> This builder also removes the
> linux_chromium_chromeos_ozone_rel_ng builder from the CQ
> since would otherwise be redundant with the
> linux_chromium_chromeos_rel_ng builder.
>
> This CL also removes a couple of commented-out CQ entries for
> builders that were removed as part of the work in bug 669297
> (linux_chromium_chromeos_compile_dbg_ng and linux_chromium_clobber_rel_ng);
> at the time I had planned to re-add them once the capacity
> issues were resolved, but at this point it's unclear how
> important those configs are and we may want to use the
> capacity for other things, and so these comments were misleading.

BUG= 671355 ,  742623 
R=kylechar@chromium.org
TBR=achuith@chromium.org, xdai@chromium.org
CQ_INCLUDE_TRYBOTS=master.tryserver.chromium.linux:linux_chromium_chromeos_asan_rel_ng,linux_chromium_chromeos_msan_rel_ng

Change-Id: I27377846c8a7ad915b68ca99abb944de58631683
Reviewed-on: https://chromium-review.googlesource.com/571195
Reviewed-by: Dirk Pranke <dpranke@chromium.org>
Reviewed-by: kylechar <kylechar@chromium.org>
Commit-Queue: Dirk Pranke <dpranke@chromium.org>
Cr-Commit-Position: refs/heads/master@{#486768}
[modify] https://crrev.com/63e34448474381620aa6fce8c68b7f2c4ced7b75/chrome/browser/chromeos/login/bluetooth_host_pairing_browsertest.cc
[modify] https://crrev.com/63e34448474381620aa6fce8c68b7f2c4ced7b75/infra/config/cq.cfg
[modify] https://crrev.com/63e34448474381620aa6fce8c68b7f2c4ced7b75/testing/buildbot/chromium.chromiumos.json
[modify] https://crrev.com/63e34448474381620aa6fce8c68b7f2c4ced7b75/testing/buildbot/chromium.memory.json
[modify] https://crrev.com/63e34448474381620aa6fce8c68b7f2c4ced7b75/tools/mb/mb_config.pyl

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/81988fa8f6fde29a33b0d22c57c440be7ef50b4c

commit 81988fa8f6fde29a33b0d22c57c440be7ef50b4c
Author: Dirk Pranke <dpranke@chromium.org>
Date: Fri Jul 14 21:32:00 2017

Attempt to fix chromium.gpu.fyi/Linux ChromiumOS Ozone Builder.

My change in #486768 looks to have broken the Linux Chromium Ozone
Builder which, confusingly, doesn't actually seem to be building
ChromiumOS, but rather, a variant of the desktop linux build
that uses Linux + Ozone + the system libdrm and libgbm libs.

TBR=jmadill@chromium.org, kbr@chromium.org
NOTRY=true
BUG= 671355 

Change-Id: I99d7501f9821eaae10affd999790b9bc87369f2a
Reviewed-on: https://chromium-review.googlesource.com/572301
Reviewed-by: Dirk Pranke <dpranke@chromium.org>
Commit-Queue: Dirk Pranke <dpranke@chromium.org>
Cr-Commit-Position: refs/heads/master@{#486894}
[modify] https://crrev.com/81988fa8f6fde29a33b0d22c57c440be7ef50b4c/tools/mb/mb_config.pyl

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/8729af596e1da9ce678ba5d037dd467d54aa1999

commit 8729af596e1da9ce678ba5d037dd467d54aa1999
Author: Dirk Pranke <dpranke@chromium.org>
Date: Fri Jul 14 23:10:24 2017

Attempt to fix chromium.gpu.fyi/Linux ChromiumOS Builder.

My change in #486768 flipped this builder from ChomeOS/X11 to
ChromeOS/Ozone, but it looks like that config may not successfully
build 'All' correctly. This change reverts the config for that
particular builder (so that we keep building X11 for now), but
we need to fix the build so that it is using Ozone instead.

TBR=kbr@chromium.org, jmadill@chromium.org, kylechar@chromium.org, fhenigman@chromium.org
NOTRY=true
BUG= 671355 ,  743257 

Change-Id: Ic4739ef28a35fa556c662ba19221530217f0556f
Reviewed-on: https://chromium-review.googlesource.com/572384
Commit-Queue: Dirk Pranke <dpranke@chromium.org>
Reviewed-by: kylechar <kylechar@chromium.org>
Reviewed-by: Dirk Pranke <dpranke@chromium.org>
Cr-Commit-Position: refs/heads/master@{#486917}
[modify] https://crrev.com/8729af596e1da9ce678ba5d037dd467d54aa1999/tools/mb/mb_config.pyl

I think at this point the only thing left build X11 CrOS is chromium.gpu.fyi Linux ChromiumOS Builder. Once that is switched to Ozone CrOS then all X11 specific code will be dead.

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/04df1cd8908fddf05ee07df51dd9f7c49c19e009

commit 04df1cd8908fddf05ee07df51dd9f7c49c19e009
Author: kylechar <kylechar@chromium.org>
Date: Sat Jul 29 02:28:18 2017

Intentionally break X11 CrOS build.

I don't think any trybots still build X11 CrOS, let's double check by
intentionally breaking the configuration. If this doesn't get reverted
then X11 CrOS is officially dead.

Bug:  671355 
Change-Id: I31be7cb75c35639d5254d16aa0a9290304b1faf3
Reviewed-on: https://chromium-review.googlesource.com/591784
Reviewed-by: Elliot Glaysher <erg@chromium.org>
Reviewed-by: Scott Violet <sky@chromium.org>
Reviewed-by: Dirk Pranke <dpranke@chromium.org>
Commit-Queue: kylechar <kylechar@chromium.org>
Cr-Commit-Position: refs/heads/master@{#490588}
[modify] https://crrev.com/04df1cd8908fddf05ee07df51dd9f7c49c19e009/ash/BUILD.gn

I've filled  issue 750642  for the task of cleaning up dead code.

I think it's safe to say that X11 CrOS has been deprecated. It no longer compiles and most X11 CrOS specific code is gone. I'll leave  issue 750642  open for any remaining cleanup.