This will involve ensuring that chrome_public_test_apk is:
 1) fast enough
 2) stable enough

to run on the CQ.

Is there anything stopping chrome_public_test_apk being turned on for android_n5x_swarming_rel?

No, there is no blocking on it. Was keeping monitoring if the build was stable enough (before holiday). Try run results showed not stable until 6/29:

https://chromium-swarm.appspot.com/tasklist?c=name&c=state&c=created_ts&c=user&c=bot&c=duration&et=1498241280000&f=name%3Achrome_public_test_apk&f=buildername%3Aandroid_n5x_swarming_rel&l=50&n=true&s=created_ts%3Adesc&st=1497982080000

Will try run more times today, and is able to add if it keeps looking good.

CL is: https://codereview.chromium.org/2942113002 (btw, the cl is lack of lgtm from jbudorick who is ooo until Thursday)

Created a test failure tasks tracking file:
https://docs.google.com/a/google.com/document/d/1LCPTGVBZrrgHh3sZCrqwyzTOqMff72OIrwQv5wFjq6I/edit?usp=sharing

Based on the test results, currently need to add @DisabledTest to tests:
org.chromium.chrome.browser.widget.OverviewListLayoutTest#testCanSwipeClosed
org.chromium.chrome.browser.payments.PaymentRequestJourneyLoggerTest#testNumberOfSuggestionsShown_ShippingAddress_Completed

And add @RetryOnFailure to tests:
org.chromium.chrome.browser.omnibox.OmniboxTest#testRequestZeroSuggestTypeAndBackspace
org.chromium.chrome.browser.hardware_acceleration.ToastHWATest#testOpenedInBackgroundToast

Update: based on discussion in CL https://codereview.chromium.org/2991433002/, mark @RetryOnFailure to all the 4 tests above.

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/b21cd269550a2a5cb229d7bf055d1039811e32a2

commit b21cd269550a2a5cb229d7bf055d1039811e32a2
Author: shenghuazhang <shenghuazhang@chromium.org>
Date: Mon Jul 24 19:17:32 2017

[Tests] Add @RetryOnFailure to tests

Based on running chrome_public_test_apk on android_n5x_swarming_rel test results, currently need to add @RetryOnFailure to tests:
OverviewListLayoutTest#testCanSwipeClosed
PaymentRequestJourneyLoggerTest#testNumberOfSuggestionsShown_ShippingAddress_Completed
OmniboxTest#testRequestZeroSuggestTypeAndBackspace
ToastHWATest#testOpenedInBackgroundToast

BUG=731759

Review-Url: https://codereview.chromium.org/2991433002
Cr-Commit-Position: refs/heads/master@{#489044}

[modify] https://crrev.com/b21cd269550a2a5cb229d7bf055d1039811e32a2/chrome/android/javatests/src/org/chromium/chrome/browser/hardware_acceleration/ToastHWATest.java
[modify] https://crrev.com/b21cd269550a2a5cb229d7bf055d1039811e32a2/chrome/android/javatests/src/org/chromium/chrome/browser/omnibox/OmniboxTest.java
[modify] https://crrev.com/b21cd269550a2a5cb229d7bf055d1039811e32a2/chrome/android/javatests/src/org/chromium/chrome/browser/payments/PaymentRequestJourneyLoggerTest.java
[modify] https://crrev.com/b21cd269550a2a5cb229d7bf055d1039811e32a2/chrome/android/javatests/src/org/chromium/chrome/browser/widget/OverviewListLayoutTest.java

After the CL above, ran more tests on bot:
https://chromium-swarm.appspot.com/tasklist?c=name&c=state&c=created_ts&c=user&c=bot&c=duration&et=1498241280000&f=name%3Achrome_public_test_apk&f=buildername%3Aandroid_n5x_swarming_rel&l=50&n=true&s=created_ts%3Adesc&st=1497982080000

Results turn out to be 2 one time tests failures in the 20 try runs. Discussed with @jbudorick offline, add @RetryOnFailure to those one time failed tests for now, and keep tracking try-run results.

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/d5292452b2f2be80fbdd27b89be6be3cae978e3c

commit d5292452b2f2be80fbdd27b89be6be3cae978e3c
Author: shenghuazhang <shenghuazhang@chromium.org>
Date: Wed Jul 26 19:18:28 2017

[Android] Add @RetryOnFailure to chrome_public_test_apk tests

Running chrome_public_test_apk on bot android_n5x_swarming_rel results
turns out to some one time failure tests. This cl add @RetryOnFailure to
some of the failure tests:
    BrowsingDataBridgeTest#testNoCalls
    UndoBarControllerTest#testCloseAll_MultipleTabs_Undo

Based on result tasks:
https://build.chromium.org/p/tryserver.chromium.android/builders/android_n5x_swarming_rel/builds/227871
https://build.chromium.org/p/tryserver.chromium.android/builders/android_n5x_swarming_rel/builds/227883

BUG=731759

Review-Url: https://codereview.chromium.org/2988833002
Cr-Commit-Position: refs/heads/master@{#489721}

[modify] https://crrev.com/d5292452b2f2be80fbdd27b89be6be3cae978e3c/chrome/android/javatests/src/org/chromium/chrome/browser/preferences/privacy/BrowsingDataBridgeTest.java
[modify] https://crrev.com/d5292452b2f2be80fbdd27b89be6be3cae978e3c/chrome/android/javatests/src/org/chromium/chrome/browser/snackbar/undo/UndoBarControllerTest.java

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/3400947e6579ff72a2b6599a94e389bc3156b258

commit 3400947e6579ff72a2b6599a94e389bc3156b258
Author: John Budorick <jbudorick@chromium.org>
Date: Tue Apr 03 17:38:44 2018

Run chrome_public_test_apk at 100% experiment on android_n5x_swarming_rel.

Bug: 731759
Change-Id: Ied650ef11b381acf050fb606a06670fe78e187de
Reviewed-on: https://chromium-review.googlesource.com/920682
Reviewed-by: Benjamin Pastene <bpastene@chromium.org>
Commit-Queue: John Budorick <jbudorick@chromium.org>
Cr-Commit-Position: refs/heads/master@{#547753}
[modify] https://crrev.com/3400947e6579ff72a2b6599a94e389bc3156b258/testing/buildbot/chromium.android.json
[modify] https://crrev.com/3400947e6579ff72a2b6599a94e389bc3156b258/testing/buildbot/chromium.swarm.json
[modify] https://crrev.com/3400947e6579ff72a2b6599a94e389bc3156b258/testing/buildbot/test_suite_exceptions.pyl

We now have a few months of experiment data -- can the test be enabled?

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/a789de205b989af84fb68e67948311d67d071cfa

commit a789de205b989af84fb68e67948311d67d071cfa
Author: Ben Pastene <bpastene@chromium.org>
Date: Tue Oct 30 02:22:23 2018

Add chrome_public_test_apk to android-marshmallow-arm64-rel at 50% experiment.

Capacity's been refreshed. Let's see if we got enough.

Bug: 877280, 731759
Change-Id: Iadf72d1220133710c618bbb5468d4a30facf6955
Reviewed-on: https://chromium-review.googlesource.com/c/1306843
Reviewed-by: John Budorick <jbudorick@chromium.org>
Commit-Queue: Ben Pastene <bpastene@chromium.org>
Cr-Commit-Position: refs/heads/master@{#603745}
[modify] https://crrev.com/a789de205b989af84fb68e67948311d67d071cfa/testing/buildbot/chromium.android.json
[modify] https://crrev.com/a789de205b989af84fb68e67948311d67d071cfa/testing/buildbot/test_suite_exceptions.pyl