xidachen@, could you take a look?
Crash logs look the same as  Issue 869337  and  Issue 867858 .

Disabling the test on https://chromium-review.googlesource.com/c/chromium/src/+/1166602.

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/90e9d5ae2819bb58b64d0525cacc8754cfd595b6

commit 90e9d5ae2819bb58b64d0525cacc8754cfd595b6
Author: W. James MacLean <wjmaclean@chromium.org>
Date: Mon Sep 10 20:40:41 2018

Tentatively re-enable SitePerProcessHitTestBrowserTest.TouchActionAckTimeout

A number of changes have landed recently that may eliminate the
flakieness seen in this test. This CL re-enables the test, but feel
free to revert this if the flakes continue.

Bug:  871062 
Change-Id: Iad353f9aecbf2eb59c4831ef70658f08c13a47a9
Reviewed-on: https://chromium-review.googlesource.com/1217087
Reviewed-by: Ken Buchanan <kenrb@chromium.org>
Commit-Queue: James MacLean <wjmaclean@chromium.org>
Cr-Commit-Position: refs/heads/master@{#590047}
[modify] https://crrev.com/90e9d5ae2819bb58b64d0525cacc8754cfd595b6/content/browser/site_per_process_hit_test_browsertest.cc

Looks like it's still flaky.

https://test-results.appspot.com/dashboards/flakiness_dashboard.html#testType=content_browsertests&tests=SitePerProcessHitTestBrowserTest.TouchActionAckTimeout%2F0

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/5e9182dc74a1b3a85920bb9c99c19dbb2354a885

commit 5e9182dc74a1b3a85920bb9c99c19dbb2354a885
Author: Yutaka Hirano <yhirano@chromium.org>
Date: Tue Sep 11 07:38:37 2018

Revert "Tentatively re-enable SitePerProcessHitTestBrowserTest.TouchActionAckTimeout"

This reverts commit 90e9d5ae2819bb58b64d0525cacc8754cfd595b6.

Reason for revert: The test is still flaky.

Original change's description:
> Tentatively re-enable SitePerProcessHitTestBrowserTest.TouchActionAckTimeout
> 
> A number of changes have landed recently that may eliminate the
> flakieness seen in this test. This CL re-enables the test, but feel
> free to revert this if the flakes continue.
> 
> Bug:  871062 
> Change-Id: Iad353f9aecbf2eb59c4831ef70658f08c13a47a9
> Reviewed-on: https://chromium-review.googlesource.com/1217087
> Reviewed-by: Ken Buchanan <kenrb@chromium.org>
> Commit-Queue: James MacLean <wjmaclean@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#590047}

TBR=kenrb@chromium.org,wjmaclean@chromium.org

Change-Id: I7467a05dc55da2a98e0e5476bb4088e64ffb7d01
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug:  871062 
Reviewed-on: https://chromium-review.googlesource.com/1218306
Reviewed-by: Yutaka Hirano <yhirano@chromium.org>
Commit-Queue: Yutaka Hirano <yhirano@chromium.org>
Cr-Commit-Position: refs/heads/master@{#590226}
[modify] https://crrev.com/5e9182dc74a1b3a85920bb9c99c19dbb2354a885/content/browser/site_per_process_hit_test_browsertest.cc

Detected 7 new flakes for test/step "SitePerProcessHitTestBrowserTest.TouchActionAckTimeout/0". To see the actual flakes, please visit https://chromium-try-flakes.appspot.com/all_flake_occurrences?key=ahVzfmNocm9taXVtLXRyeS1mbGFrZXNyQwsSBUZsYWtlIjhTaXRlUGVyUHJvY2Vzc0hpdFRlc3RCcm93c2VyVGVzdC5Ub3VjaEFjdGlvbkFja1RpbWVvdXQvMAw. This message was posted automatically by the chromium-try-flakes app. Since flakiness is ongoing, the issue was moved back into Sheriff Bug Queue (unless already there).

The new flakes seem specific to the /0 and /1 variants of the test.

https://test-results.appspot.com/dashboards/flakiness_dashboard.html#testType=content_browsertests&tests=SitePerProcessHitTestBrowserTest.TouchActionAckTimeout

In a recent log from

https://chromium-swarm.appspot.com/task?id=3fe07fda58d4d710&refresh=10&show_raw=1 

on the Marshmallow 64 bot

https://ci.chromium.org/p/chromium/builders/luci.chromium.ci/Marshmallow%2064%20bit%20Tester/23775

We see the failure is due to a failed check:

I  583.569s run_tests_on_device(01e89883aed2c8a9)  [ RUN      ] SitePerProcessHitTestBrowserTest.TouchActionAckTimeout/0
I  583.569s run_tests_on_device(01e89883aed2c8a9)  [WARNING:dns_config_service_posix.cc(333)] Failed to read DnsConfig.
I  583.569s run_tests_on_device(01e89883aed2c8a9)  [WARNING:child_process_launcher_helper_posix.cc(120)] Ignoring invalid file assets/snapshot_blob_32.bin
I  583.569s run_tests_on_device(01e89883aed2c8a9)  [WARNING:simple_synchronous_entry.cc(1252)] Could not open platform files for entry.
I  583.569s run_tests_on_device(01e89883aed2c8a9)  [WARNING:child_process_launcher_helper_posix.cc(120)] Ignoring invalid file assets/snapshot_blob_32.bin
I  583.569s run_tests_on_device(01e89883aed2c8a9)  [WARNING:child_process_launcher_helper_posix.cc(120)] Ignoring invalid file assets/snapshot_blob_32.bin
I  583.569s run_tests_on_device(01e89883aed2c8a9)  [FATAL:input_event_stream_validator.cc(34)] Check failed: ValidateImpl(event, fling_cancellation_is_deferred, &error_msg_). Missing tap ending event before TapDown
I  583.570s run_tests_on_device(01e89883aed2c8a9)  
I  583.570s run_tests_on_device(01e89883aed2c8a9)  Invalid Event: GestureTapDown (Time: 8575.920000, Modifiers: 0)
I  583.570s run_tests_on_device(01e89883aed2c8a9)  {
I  583.570s run_tests_on_device(01e89883aed2c8a9)   Pos: (24.000000, 24.000000)
I  583.570s run_tests_on_device(01e89883aed2c8a9)   GlobalPos: (32.000000, 32.000000)
I  583.570s run_tests_on_device(01e89883aed2c8a9)   SourceDevice: 2
I  583.570s run_tests_on_device(01e89883aed2c8a9)   RawData: (20.000000, 20.000000, 0.000000, 0.000000, 0)
I  583.570s run_tests_on_device(01e89883aed2c8a9)  }

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/25df0ee376cf548672aea30066cea6f7c6a40047

commit 25df0ee376cf548672aea30066cea6f7c6a40047
Author: Xida Chen <xidachen@chromium.org>
Date: Fri Sep 14 02:27:22 2018

Deflake TouchActionAckTimeout

Currently this test is flaky because we do not wait for the ack of the
touch start from the main thread.

This CL fixes this issue by using a ack waiter, to ensure that the ack
from the main thread has arrived.

TBR=alexmos@chromium.org

Bug:  871062 
Change-Id: Ia883bcbb1b483d8fb481ce88dd5c947ea623d506
Reviewed-on: https://chromium-review.googlesource.com/1221476
Commit-Queue: Xida Chen <xidachen@chromium.org>
Reviewed-by: James MacLean <wjmaclean@chromium.org>
Cr-Commit-Position: refs/heads/master@{#591271}
[modify] https://crrev.com/25df0ee376cf548672aea30066cea6f7c6a40047/content/browser/site_per_process_hit_test_browsertest.cc

Thanks Xida!